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  • Learning Python else syntax error

    - by user1441016
    Hi I am learning python by doing the practice problems for Open course at MIT 6.00 Intro to Computer Science. I am Trying to do practice problem 1 part 2 create a recursive function to count the instance of key in target. My code so far... from string import * def countSubStringMatchRecursive (target, key,x,s): if (find(target,key)==find(target,key,s)) and (find(target,key)==find(target,key,(find(target,key)))):#if first and last return (1) elif (find(target,key)==find(target,key,s))and (find(target,key)!=find(target,key,(find(target,key)))):#if first but not last x=1 s= find(target,key) return (countSubStringMatchRecursive(target,key,s,x) elif (find(target,key,s))==-1 and (find(target,key)!=find(target,key,s)):#if last but not first return (x+1) elif:(find(target,key,s))!=-1 and (find(target,key)!=find(target,key,s)):#if not last and not first x=x+1 s= find(target,key,s) return (countSubStringMatchRecursive(target,key,s,x) I getting a syntax error at line 8. I would just like to know what I did wrong there. Dont worry about the other mistakes I should be able to get those sorted out. I just Stuck on this. Thanks.

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  • Python OOP - object has no attribute

    - by user1744269
    I am attempting to learn how to program. I really do want to learn how to program; I love the building and design aspect of it. However, in Java and Python, I have tried and failed with programs as they pertain to objects, classes, methods.. I am trying to develop some code for a program, but im stumped. I know this is a simple error. However I am lost! I am hoping someone can guide me to a working program, but also help me learn (criticism is not only expected, but APPRECIATED). class Converter: def cTOf(self, numFrom): numFrom = self.numFrom numTo = (self.numFrom * (9/5)) + 32 print (str(numTo) + ' degrees Farenheit') return numTo def fTOc(self, numFrom): numFrom = self.numFrom numTo = ((numFrom - 32) * (5/9)) return numTo convert = Converter() numFrom = (float(input('Enter a number to convert.. '))) unitFrom = input('What unit would you like to convert from.. ') unitTo = input('What unit would you like to convert to.. ') if unitFrom == ('celcius'): convert.cTOf(numFrom) print(numTo) input('Please hit enter..') if unitFrom == ('farenheit'): convert.fTOc(numFrom) print(numTo) input('Please hit enter..')

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  • Parallel Classloading Revisited: Fully Concurrent Loading

    - by davidholmes
    Java 7 introduced support for parallel classloading. A description of that project and its goals can be found here: http://openjdk.java.net/groups/core-libs/ClassLoaderProposal.html The solution for parallel classloading was to add to each class loader a ConcurrentHashMap, referenced through a new field, parallelLockMap. This contains a mapping from class names to Objects to use as a classloading lock for that class name. This was then used in the following way: protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException { synchronized (getClassLoadingLock(name)) { // First, check if the class has already been loaded Class c = findLoadedClass(name); if (c == null) { long t0 = System.nanoTime(); try { if (parent != null) { c = parent.loadClass(name, false); } else { c = findBootstrapClassOrNull(name); } } catch (ClassNotFoundException e) { // ClassNotFoundException thrown if class not found // from the non-null parent class loader } if (c == null) { // If still not found, then invoke findClass in order // to find the class. long t1 = System.nanoTime(); c = findClass(name); // this is the defining class loader; record the stats sun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0); sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1); sun.misc.PerfCounter.getFindClasses().increment(); } } if (resolve) { resolveClass(c); } return c; } } Where getClassLoadingLock simply does: protected Object getClassLoadingLock(String className) { Object lock = this; if (parallelLockMap != null) { Object newLock = new Object(); lock = parallelLockMap.putIfAbsent(className, newLock); if (lock == null) { lock = newLock; } } return lock; } This approach is very inefficient in terms of the space used per map and the number of maps. First, there is a map per-classloader. As per the code above under normal delegation the current classloader creates and acquires a lock for the given class, checks if it is already loaded, then asks its parent to load it; the parent in turn creates another lock in its own map, checks if the class is already loaded and then delegates to its parent and so on till the boot loader is invoked for which there is no map and no lock. So even in the simplest of applications, you will have two maps (in the system and extensions loaders) for every class that has to be loaded transitively from the application's main class. If you knew before hand which loader would actually load the class the locking would only need to be performed in that loader. As it stands the locking is completely unnecessary for all classes loaded by the boot loader. Secondly, once loading has completed and findClass will return the class, the lock and the map entry is completely unnecessary. But as it stands, the lock objects and their associated entries are never removed from the map. It is worth understanding exactly what the locking is intended to achieve, as this will help us understand potential remedies to the above inefficiencies. Given this is the support for parallel classloading, the class loader itself is unlikely to need to guard against concurrent load attempts - and if that were not the case it is likely that the classloader would need a different means to protect itself rather than a lock per class. Ultimately when a class file is located and the class has to be loaded, defineClass is called which calls into the VM - the VM does not require any locking at the Java level and uses its own mutexes for guarding its internal data structures (such as the system dictionary). The classloader locking is primarily needed to address the following situation: if two threads attempt to load the same class, one will initiate the request through the appropriate loader and eventually cause defineClass to be invoked. Meanwhile the second attempt will block trying to acquire the lock. Once the class is loaded the first thread will release the lock, allowing the second to acquire it. The second thread then sees that the class has now been loaded and will return that class. Neither thread can tell which did the loading and they both continue successfully. Consider if no lock was acquired in the classloader. Both threads will eventually locate the file for the class, read in the bytecodes and call defineClass to actually load the class. In this case the first to call defineClass will succeed, while the second will encounter an exception due to an attempted redefinition of an existing class. It is solely for this error condition that the lock has to be used. (Note that parallel capable classloaders should not need to be doing old deadlock-avoidance tricks like doing a wait() on the lock object\!). There are a number of obvious things we can try to solve this problem and they basically take three forms: Remove the need for locking. This might be achieved by having a new version of defineClass which acts like defineClassIfNotPresent - simply returning an existing Class rather than triggering an exception. Increase the coarseness of locking to reduce the number of lock objects and/or maps. For example, using a single shared lockMap instead of a per-loader lockMap. Reduce the lifetime of lock objects so that entries are removed from the map when no longer needed (eg remove after loading, use weak references to the lock objects and cleanup the map periodically). There are pros and cons to each of these approaches. Unfortunately a significant "con" is that the API introduced in Java 7 to support parallel classloading has essentially mandated that these locks do in fact exist, and they are accessible to the application code (indirectly through the classloader if it exposes them - which a custom loader might do - and regardless they are accessible to custom classloaders). So while we can reason that we could do parallel classloading with no locking, we can not implement this without breaking the specification for parallel classloading that was put in place for Java 7. Similarly we might reason that we can remove a mapping (and the lock object) because the class is already loaded, but this would again violate the specification because it can be reasoned that the following assertion should hold true: Object lock1 = loader.getClassLoadingLock(name); loader.loadClass(name); Object lock2 = loader.getClassLoadingLock(name); assert lock1 == lock2; Without modifying the specification, or at least doing some creative wordsmithing on it, options 1 and 3 are precluded. Even then there are caveats, for example if findLoadedClass is not atomic with respect to defineClass, then you can have concurrent calls to findLoadedClass from different threads and that could be expensive (this is also an argument against moving findLoadedClass outside the locked region - it may speed up the common case where the class is already loaded, but the cost of re-executing after acquiring the lock could be prohibitive. Even option 2 might need some wordsmithing on the specification because the specification for getClassLoadingLock states "returns a dedicated object associated with the specified class name". The question is, what does "dedicated" mean here? Does it mean unique in the sense that the returned object is only associated with the given class in the current loader? Or can the object actually guard loading of multiple classes, possibly across different class loaders? So it seems that changing the specification will be inevitable if we wish to do something here. In which case lets go for something that more cleanly defines what we want to be doing: fully concurrent class-loading. Note: defineClassIfNotPresent is already implemented in the VM as find_or_define_class. It is only used if the AllowParallelDefineClass flag is set. This gives us an easy hook into existing VM mechanics. Proposal: Fully Concurrent ClassLoaders The proposal is that we expand on the notion of a parallel capable class loader and define a "fully concurrent parallel capable class loader" or fully concurrent loader, for short. A fully concurrent loader uses no synchronization in loadClass and the VM uses the "parallel define class" mechanism. For a fully concurrent loader getClassLoadingLock() can return null (or perhaps not - it doesn't matter as we won't use the result anyway). At present we have not made any changes to this method. All the parallel capable JDK classloaders become fully concurrent loaders. This doesn't require any code re-design as none of the mechanisms implemented rely on the per-name locking provided by the parallelLockMap. This seems to give us a path to remove all locking at the Java level during classloading, while retaining full compatibility with Java 7 parallel capable loaders. Fully concurrent loaders will still encounter the performance penalty associated with concurrent attempts to find and prepare a class's bytecode for definition by the VM. What this penalty is depends on the number of concurrent load attempts possible (a function of the number of threads and the application logic, and dependent on the number of processors), and the costs associated with finding and preparing the bytecodes. This obviously has to be measured across a range of applications. Preliminary webrevs: http://cr.openjdk.java.net/~dholmes/concurrent-loaders/webrev.hotspot/ http://cr.openjdk.java.net/~dholmes/concurrent-loaders/webrev.jdk/ Please direct all comments to the mailing list [email protected].

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  • How could there still not be a mysqldb module for Python 3? [closed]

    - by itsadok
    This SO question is now more than two years old. MySQL is an incredibly popular database engine, Python is an incredibly popular programming language, and Python 3 has been officially released two years ago, and was available even before that. What's more, the whole mysqldb module is just a layer translating Python's db-api to MySQL's API. It's not that big of a library. I must be missing something here. How come almost* nobody in the entire open source community has spent the (I'm guessing) two weeks it takes to port this lib? Is Python 3 that unpopular? Is the combination of python and mysql not as common as I assume? Or maybe it's just a lot harder to port mysqldb than I assume? Anyone know the inside story on this? * Now I see that this guy has done it, which takes some of the wind out of my question, but it still seems to little and too late to make sense. EDIT: OK, I'm aware that the stock answers for these kind of questions cover this one as well. Patches welcome, scratch your itch, we don't work for you and we don't have the time, etc. I actually took a shot at porting this about a year ago, but it was my first time doing anything with Python C extensions, and I failed. My point in writing this was not a plea for somebody to write it, but genuine curiosity: it seems that some much more complicated libraries have been ported to python 3 already, and in the poll for which libraries should be ported, mysqldb is not even nominated! That suggests that maybe (2) is the right answer. UPDATE: I found that there are several new libraries that provide mysql support under Python 3, I just wasn't googling hard enough. That explains everything.

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  • Does python import all the listed libraries? - Python

    - by RadiantHex
    Hi folks, I'm just wondering, I often have really long python files and imports tend to stack quite quickly. PEP8 says that the imports should always be written at the beginning of the file. Do all the imported libraries get imported when calling a function coded in the file? Or do only the necessary libraries get called? Does it make sense to worry about this? Is there no reason to import libraries within the functions or classes that need them?

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  • Replacing words in string

    - by abkai
    Okay, so I have the following little function: def swap(inp): inp = inp.split() out = "" for item in inp: ind = inp.index(item) item = item.replace("i am", "you are") item = item.replace("you are", "I am") item = item.replace("i'm", "you're") item = item.replace("you're", "I'm") item = item.replace("my", "your") item = item.replace("your", "my") item = item.replace("you", "I") item = item.replace("my", "your") item = item.replace("i", "you") inp[ind] = item for item in inp: ind = inp.index(item) item = item + " " inp[ind] = item return out.join(inp) Which, while it's not particularly efficient gets the job done for shorter sentences. Basically, all it does is swaps pronoun etc. perspectives. This is fine when I throw a string like "I love you" at it, it returns "you love me" but when I throw something like: you love your version of my couch because I love you, and you're a couch-lover. I get: I love your versyouon of your couch because I love I, and I'm a couch-lover. I'm confused as to why this is happening. I explicitly split the string into a list to avoid this. Why would it be able to detect it as being a part of a list item, rather than just an exact match? Also, slightly deviating to avoid having to post another question so similar; if a solution to this breaks this function, what will happen to commas, full stops, other punctuation? It made some very surprising mistakes. My expected output is: I love my version of your couch because you love I, and I'm a couch-lover. The reason I formatted it like this, is because I eventually hope to be able to replace the item.replace(x, y) variables with words in a database.

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  • It says i have an indented block when i dont?

    - by user3728373
    def cave(): global key global response print(''' You find yourself standing infront of a cave. You venture into the cave to find a large door blocking your path. (insert key, turn around''') response = input("Enter a command: ") while response != 'insert key' or response != 'turn around': if response =='insert key' or response == 'turn around': break print('Choose one of the options: ") response = input() if response == 'insert key': if key == 1: win() else: print('''You don't have a key. Get One!!''') elif response == 'turn around' : home()

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  • In parallel.for share value more then one.

    - by user347918
    Here is problem. long sum = 0; Parallel.For(1, 10000, y => { sum1 += y;} ); Solution is .. Parallel.For<int>(0, result.Count, () => 0, (i, loop, subtotal) => { subtotal += result[i]; return subtotal; }, (x) => Interlocked.Add(ref sum, x) ); if there are two parameters in this code. For example long sum1 = 0; long sum2 = 0; Parallel.For(1, 10000, y => { sum1 += y; sum2=sum1*y; } ); what will we do ? i am guessing that have to use array ! int[] s=new int[2]; Parallel.For<int[]>(0, result.Count, () => s, (i, loop, subtotal) => { subtotal[0] += result[i]; subtotal[1] -= result[i]; return subtotal; }, (x) => Interlocked.Add(ref sum1, x[0]) //but how about sum1 i tried several way but it doesn't work. //for example like that //(x[0])=> Interlocked.Add (ref sum1, x[0]) //(x[1])=> Interlocked.Add (ref sum2, x[1]));

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  • Parallel doseq for Clojure

    - by andrew cooke
    I haven't used multithreading in Clojure at all so am unsure where to start. I have a doseq whose body can run in parallel. What I'd like is for there always to be 3 threads running (leaving 1 core free) that evaluate the body in parallel until the range is exhausted. There's no shared state, nothing complicated - the equivalent of Python's multiprocessing would be just fine. So something like: (dopar 3 [i (range 100)] ; repeated 100 times in 3 parallel threads... ...) Where should I start looking? Is there a command for this? A standard package? A good reference? So far I have found pmap, and could use that (how do I restrict to 3 at a time? looks like it uses 32 at a time - no, source says 2 + number of processors), but it seems like this is a basic primitive that should already exist somewhere. clarification: I really would like to control the number of threads. I have processes that are long-running and use a fair amount of memory, so creating a large number and hoping things work out OK isn't a good approach (example which uses a significant chunk available mem). update: Starting to write a macro that does this, and I need a semaphore (or a mutex, or an atom i can wait on). Do semaphores exist in Clojure? Or should I use a ThreadPoolExecutor? It seems odd to have to pull so much in from Java - I thought parallel programming in Clojure was supposed to be easy... Maybe I am thinking about this completely the wrong way? Hmmm. Agents?

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  • .NET 4 ... Parallel.ForEach() question

    - by CirrusFlyer
    I understand that the new TPL (Task Parallel Library) has implemented the Parallel.ForEach() such that it works with "expressed parallelism." Meaning, it does not guarantee that your delegates will run in multiple threads, but rather it checks to see if the host platform has multiple cores, and if true, only then does it distribute the work across the cores (essentially 1 thread per core). If the host system does not have multiple cores (getting harder and harder to find such a computer) then it will run your code sequenceally like a "regular" foreach loop would. Pretty cool stuff, frankly. Normally I would do something like the following to place my long running operation on a background thread from the ThreadPool: ThreadPool.QueueUserWorkItem( new WaitCallback(targetMethod), new Object2PassIn() ); In a situation whereby the host computer only has a single core does the TPL's Parallel.ForEach() automatically place the invocation on a background thread? Or, should I manaully invoke any TPL calls from a background thead so that if I am executing from a single core computer at least that logic will be off of the GUI's dispatching thread? My concern is if I leave the TPL in charge of all this I want to ensure if it determines it's a single core box that it still marshalls the code that's inside of the Parallel.ForEach() loop on to a background thread like I would have done, so as to not block my GUI. Thanks for any thoughts or advice you may have ...

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  • Parallel features in .Net 4.0

    - by Jonathan.Peppers
    I have been going over the practicality of some of the new parallel features in .Net 4.0. Say I have code like so: foreach (var item in myEnumerable) myDatabase.Insert(item.ConvertToDatabase()); Imagine myDatabase.Insert is performing some work to insert to a SQL database. Theoretically you could write: Parallel.ForEach(myEnumerable, item => myDatabase.Insert(item.ConvertToDatabase())); And automatically you get code that takes advantage of multiple cores. But what if myEnumerable can only be interacted with by a single thread? Will the Parallel class enumerate by a single thread and only dispatch the result to worker threads in the loop? What if myDatabase can only be interacted with by a single thread? It would certainly not be better to make a database connection per iteration of the loop. Finally, what if my "var item" happens to be a UserControl or something that must be interacted with on the UI thread? What design pattern should I follow to solve these problems? It's looking to me that switching over to Parallel/PLinq/etc is not exactly easy when you are dealing with real-world applications.

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  • Python — Time complexity of built-in functions versus manually-built functions in finite fields

    - by stackuser
    Generally, I'm wondering about the advantages versus disadvantages of using the built-in arithmetic functions versus rolling your own in Python. Specifically, I'm taking in GF(2) finite field polynomials in string format, converting to base 2 values, performing arithmetic, then output back into polynomials as string format. So a small example of this is in multiplication: Rolling my own: def multiply(a,b): bitsa = reversed("{0:b}".format(a)) g = [(b<<i)*int(bit) for i,bit in enumerate(bitsa)] return reduce(lambda x,y: x+y,g) Versus the built-in: def multiply(a,b): # a,b are GF(2) polynomials in binary form .... return a*b #returns product of 2 polynomials in gf2 Currently, operations like multiplicative inverse (with for example 20 bit exponents) take a long time to run in my program as it's using all of Python's built-in mathematical operations like // floor division and % modulus, etc. as opposed to making my own division, remainder, etc. I'm wondering how much of a gain in efficiency and performance I can get by building these manually (as shown above). I realize the gains are dependent on how well the manual versions are built, that's not the question. I'd like to find out 'basically' how much advantage there is over the built-in's. So for instance, if multiplication (as in the example above) is well-suited for base 10 (decimal) arithmetic but has to jump through more hoops to change bases to binary and then even more hoops in operating (so it's lower efficiency), that's what I'm wondering. Like, I'm wondering if it's possible to bring the time down significantly by building them myself in ways that maybe some professionals here have already come across.

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  • Newbie, deciding Python or Erlang

    - by Joe
    Hi Guys, I'm a Administrator (unix, Linux and some windows apps such as Exchange) by experience and have never worked on any programming language besides C# and scripting on Bash and lately on powershell. I'm starting out as a service provider and using multiple network/server monitoring tools based on open source (nagios, opennms etc) in order to monitor them. At this moment, being inspired by a design that I came up with, to do more than what is available with the open source at this time, I would like to start programming and test some of these ideas. The requirement is that a server software that captures a stream of data and store them in a database(CouchDB or MongoDB preferably) and the client side (agent installed on a server) would be sending this stream of data on a schedule of every 10 minutes or so. For these two core ideas, I have been reading about Python and Erlang besides ruby. I do plan to use either Amazon or Rackspace where the server platform would run. This gives me the scalability needed when we have more customers with many servers. For that reason alone, I thought Erlang was a better fit(I could be totally wrong, new to this game) and I understand that Erlang has limited support in some ways compared to Ruby or Python. But also I'm totally new to the programming realm of things and any advise would be appreciated grately. Jo

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  • Where can I find out the following info on python (coming from Ruby)

    - by Michael Durrant
    I'm coming from Ruby and Ruby on Rails to Python. Where can I find or find resources about: The command prompt, what is python's version of 'irb' django, what is a good resource for installing, using, etc. pythoncasts... is there anything like railscats, i.e. good video tutorials web sites with the api info about what version have what and which to use. info and recommendations on editors, plugins and IDE's common gotchas for newbies and good things to know at the outset scaling issues, common reasons what is the equivalent of 'gems', i.e. components I can plug in what are popular plugins for django authentication and forms similar to devise and simple_form testing, what's available, anything similar to rspec? database adapters - any preferences? framework info - is django MVC like rails? OO'yness. Is everything an object that gets send messages? Different paradign? syntax - anything like jslint for checking for well-formed code?

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  • python: os.system does not execute shell comand

    - by capoluca
    I need to execute shell command in python program (I have ubuntu). More specifically I want to create graph using graphviz in python script. My code is os.system("dot -Tpng graph.dot -o graph.png") It does not work, but if I just type dot -Tpng graph.dot -o graph.png in command line then everything is fine. Do you know what the problem? Thank you! Edit: Does not work means that nothing happens, there are no errors. Output from dot -v -Tpng graph.dot -o graph.png: dot - graphviz version 2.26.3 (20100126.1600) Activated plugin library: libgvplugin_pango.so.6 Using textlayout: textlayout:cairo Activated plugin library: libgvplugin_dot_layout.so.6 Using layout: dot:dot_layout Using render: cairo:cairo Using device: png:cairo:cairo The plugin configuration file: /usr/lib/graphviz/config6 was successfully loaded. render : cairo dot fig gd map ps svg tk vml vrml xdot layout : circo dot fdp neato nop nop1 nop2 osage patchwork sfdp twopi textlayout : textlayout device : canon cmap cmapx cmapx_np dot eps fig gd gd2 gif gv imap imap_np ismap jpe jpeg jpg pdf plain plain-ext png ps ps2 svg svgz tk vml vmlz vrml wbmp x11 xdot xlib loadimage : (lib) eps gd gd2 gif jpe jpeg jpg png ps svg

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  • Ruby or Python?

    - by Bobby Tables
    Hi all, This question is extremely subjective and open-ended. It might even sound like something I should just research for myself and make my own decision. But I'd like to put it out there and get some thoughts from others. Long story short - I burned out with the rat race and am on a self-funded sabbatical this year. Much of it is to take a break from the corporate grind and travel around, but I also want to play around with new technologies and do some self-learning projects, to stay up to speed on programming, and well - I just love tinkering with programming, when there's no pressure! Here's the thing: I am a lifetime C/C++/Java programmer. I'm a bit of a squiggly bracket snob since I've been working with this family of languages for my entire programming career. So I'd like to learn a language which isn't so closely syntactically related to this group. What I'm basically looking for is a language which is relatively general purpose, fun to learn, has some new concepts that are different from C++/Java, and has a good community. A secondary consideration is that it has good web development frameworks. A tertiary consideration is that it's not totally academic (read: there are real world jobs out there using it). I've narrowed it down to Ruby or Python. My impression of Ruby is that it is extremely web oriented - that the only real application of it is as a server side scripting language for doing web stuff (mainly Ruby on Rails). For Python I'm not so sure. TL;DR and to put it as succinctly as possible: which of these would be better for a C++/Java guy to learn to get some new perspectives on programming? And which is more open and general purpose and applicable to a wider set of applications? I'm leaning towards Ruby at the moment, but I worry to an extent that it looks like it's used as nothing but a server side web language.

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  • How to distribute python GTK applications?

    - by Nik
    This is in correlation with the previous question I asked here. My aim is to create and package an application for easy installation in Ubuntu and other debian distributions. I understand that the best way to do this is by creating .deb file with which users can easily install my application on their system. However, I would also like to make sure my application is available in multiple languages. This is why I raised the question before which you can read here. In the answers that were provided, I was asked to use disutils for my packaging. I am however missing the bigger picture here. Why is there a need to include a setup.py file when I distribute my application in .deb format? My purpose is to ensure that users do not need to perform python setup.py to install my application but rather just click on the .deb file. I already know how to create a deb file from the excellent tutorial available here. It clearly shows how to edit rules, changelog and everything required to create a clean deb file. You can look at my application source code and folder structure at Github if it helps you better understand my situation. Please note I have glanced through the official python documentation found here. But I am hoping that I would get an answer which would help even a lame man understand since my knowledge is pretty poor in this regard.

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  • Strategies for managUse of types in Python

    - by dave
    I'm a long time programmer in C# but have been coding in Python for the past year. One of the big hurdles for me was the lack of type definitions for variables and parameters. Whereas I totally get the idea of duck typing, I do find it frustrating that I can't tell the type of a variable just by looking at it. This is an issue when you look at someone else's code where they've used ambiguous names for method parameters (see edit below). In a few cases, I've added asserts to ensure parameters comply with an expected type but this goes against the whole duck typing thing. On some methods, I'll document the expected type of parameters (eg: list of user objects), but even this seems to go against the idea of just using an object and let the runtime deal with exceptions. What strategies do you use to avoid typing problems in Python? Edit: Example of the parameter naming issues: If our code base we have a task object (ORM object) and a task_obj object (higher level object that embeds a task). Needless to say, many methods accept a parameter named 'task'. The method might expect a task or a task_obj or some other construct such as a dictionary of task properties - it is not clear. It is them up to be to look at how that parameter is used in order to work out what the method expects.

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  • Strategies for managing use of types in Python

    - by dave
    I'm a long time programmer in C# but have been coding in Python for the past year. One of the big hurdles for me was the lack of type definitions for variables and parameters. Whereas I totally get the idea of duck typing, I do find it frustrating that I can't tell the type of a variable just by looking at it. This is an issue when you look at someone else's code where they've used ambiguous names for method parameters (see edit below). In a few cases, I've added asserts to ensure parameters comply with an expected type but this goes against the whole duck typing thing. On some methods, I'll document the expected type of parameters (eg: list of user objects), but even this seems to go against the idea of just using an object and let the runtime deal with exceptions. What strategies do you use to avoid typing problems in Python? Edit: Example of the parameter naming issues: If our code base we have a task object (ORM object) and a task_obj object (higher level object that embeds a task). Needless to say, many methods accept a parameter named 'task'. The method might expect a task or a task_obj or some other construct such as a dictionary of task properties - it is not clear. It is them up to be to look at how that parameter is used in order to work out what the method expects.

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  • matplotlib and python multithread file processing

    - by Napseis
    I have a large number of files to process. I have written a script that get, sort and plot the datas I want. So far, so good. I have tested it and it gives the desired result. Then I wanted to do this using multithreading. I have looked into the doc and examples on the internet, and using one thread in my program works fine. But when I use more, at some point I get random matplotlib error, and I suspect some conflict there, even though I use a function with names for the plots, and iI can't see where the problem could be. Here is the whole script should you need more comment, i'll add them. Thank you. #!/usr/bin/python import matplotlib matplotlib.use('GTKAgg') import numpy as np from scipy.interpolate import griddata import matplotlib.pyplot as plt import matplotlib.colors as mcl from matplotlib import rc #for latex import time as tm import sys import threading import Queue #queue in 3.2 and Queue in 2.7 ! import pdb #the debugger rc('text', usetex=True)#for latex map=0 #initialize the map index. It will be use to index the array like this: array[map,[x,y]] time=np.zeros(1) #an array to store the time middle_h=np.zeros((0,3)) #x phi c #for the middle of the box current_file=open("single_void_cyl_periodic_phi_c_middle_h_out",'r') for line in current_file: if line.startswith('# === time'): map+=1 np.append(time,[float(line.strip('# === time '))]) elif line.startswith('#'): pass else: v=np.fromstring(line,dtype=float,sep=' ') middle_h=np.vstack( (middle_h,v[[1,3,4]]) ) current_file.close() middle_h=middle_h.reshape((map,-1,3)) #3d array: map, x, phi,c ##### def load_and_plot(): #will load a map file, and plot it along with the corresponding profile loaded before while not exit_flag: print("fecthing work ...") #try: if not tasks_queue.empty(): map_index=tasks_queue.get() print("----> working on map: %s" %map_index) x,y,zp=np.loadtxt("single_void_cyl_growth_periodic_post_map_"+str(map_index),unpack=True, usecols=[1, 2,3]) for i,el in enumerate(zp): if el<0.: zp[i]=0. xv=np.unique(x) yv=np.unique(y) X,Y= np.meshgrid(xv,yv) Z = griddata((x, y), zp, (X, Y),method='nearest') figure=plt.figure(num=map_index,figsize=(14, 8)) ax1=plt.subplot2grid((2,2),(0,0)) ax1.plot(middle_h[map_index,:,0],middle_h[map_index,:,1],'*b') ax1.grid(True) ax1.axis([-15, 15, 0, 1]) ax1.set_title('Profiles') ax1.set_ylabel(r'$\phi$') ax1.set_xlabel('x') ax2=plt.subplot2grid((2,2),(1,0)) ax2.plot(middle_h[map_index,:,0],middle_h[map_index,:,2],'*r') ax2.grid(True) ax2.axis([-15, 15, 0, 1]) ax2.set_ylabel('c') ax2.set_xlabel('x') ax3=plt.subplot2grid((2,2),(0,1),rowspan=2,aspect='equal') sub_contour=ax3.contourf(X,Y,Z,np.linspace(0,1,11),vmin=0.) figure.colorbar(sub_contour,ax=ax3) figure.savefig('single_void_cyl_'+str(map_index)+'.png') plt.close(map_index) tasks_queue.task_done() else: print("nothing left to do, other threads finishing,sleeping 2 seconds...") tm.sleep(2) # except: # print("failed this time: %s" %map_index+". Sleeping 2 seconds") # tm.sleep(2) ##### exit_flag=0 nb_threads=2 tasks_queue=Queue.Queue() threads_list=[] jobs=list(range(map)) #each job is composed of a map print("inserting jobs in the queue...") for job in jobs: tasks_queue.put(job) print("done") #launch the threads for i in range(nb_threads): working_bee=threading.Thread(target=load_and_plot) working_bee.daemon=True print("starting thread "+str(i)+' ...') threads_list.append(working_bee) working_bee.start() #wait for all tasks to be treated tasks_queue.join() #flip the flag, so the threads know it's time to stop exit_flag=1 for t in threads_list: print("waiting for threads %s to stop..."%t) t.join() print("all threads stopped")

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  • Python and mechanize login script

    - by Perun
    Hi fellow programmers! I am trying to write a script to login into my universities "food balance" page using python and the mechanize module... This is the page I am trying to log into: http://www.wcu.edu/11407.asp The website has the following form to login: <FORM method=post action=https://itapp.wcu.edu/BanAuthRedirector/Default.aspx><INPUT value=https://cf.wcu.edu/busafrs/catcard/idsearch.cfm type=hidden name=wcuirs_uri> <P><B>WCU ID Number<BR></B><INPUT maxLength=12 size=12 type=password name=id> </P> <P><B>PIN<BR></B><INPUT maxLength=20 type=password name=PIN> </P> <P></P> <P><INPUT value="Request Access" type=submit name=submit> </P></FORM> From this we know that I need to fill in the following fields: 1. name=id 2. name=PIN With the action: action=https://itapp.wcu.edu/BanAuthRedirector/Default.aspx This is the script I have written thus far: #!/usr/bin/python2 -W ignore import mechanize, cookielib from time import sleep url = 'http://www.wcu.edu/11407.asp' myId = '11111111111' myPin = '22222222222' # Browser #br = mechanize.Browser() #br = mechanize.Browser(factory=mechanize.DefaultFactory(i_want_broken_xhtml_support=True)) br = mechanize.Browser(factory=mechanize.RobustFactory()) # Use this because of bad html tags in the html... # Cookie Jar cj = cookielib.LWPCookieJar() br.set_cookiejar(cj) # Browser options br.set_handle_equiv(True) br.set_handle_gzip(True) br.set_handle_redirect(True) br.set_handle_referer(True) br.set_handle_robots(False) # Follows refresh 0 but not hangs on refresh > 0 br.set_handle_refresh(mechanize._http.HTTPRefreshProcessor(), max_time=1) # User-Agent (fake agent to google-chrome linux x86_64) br.addheaders = [('User-agent','Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11'), ('Accept', 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'), ('Accept-Encoding', 'gzip,deflate,sdch'), ('Accept-Language', 'en-US,en;q=0.8'), ('Accept-Charset', 'ISO-8859-1,utf-8;q=0.7,*;q=0.3')] # The site we will navigate into br.open(url) # Go though all the forms (for debugging only) for f in br.forms(): print f # Select the first (index two) form br.select_form(nr=2) # User credentials br.form['id'] = myId br.form['PIN'] = myPin br.form.action = 'https://itapp.wcu.edu/BanAuthRedirector/Default.aspx' # Login br.submit() # Wait 10 seconds sleep(10) # Save to a file f = file('mycatpage.html', 'w') f.write(br.response().read()) f.close() Now the problem... For some odd reason the page I get back (in mycatpage.html) is the login page and not the expected page that displays my "cat cash balance" and "number of block meals" left... Does anyone have any idea why? Keep in mind that everything is correct with the header files and while the id and pass are not really 111111111 and 222222222, the correct values do work with the website (using a browser...) Thanks in advance EDIT Another script I tried: from urllib import urlopen, urlencode import urllib2 import httplib url = 'https://itapp.wcu.edu/BanAuthRedirector/Default.aspx' myId = 'xxxxxxxx' myPin = 'xxxxxxxx' data = { 'id':myId, 'PIN':myPin, 'submit':'Request Access', 'wcuirs_uri':'https://cf.wcu.edu/busafrs/catcard/idsearch.cfm' } opener = urllib2.build_opener() opener.addheaders = [('User-agent','Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11'), ('Accept', 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'), ('Accept-Encoding', 'gzip,deflate,sdch'), ('Accept-Language', 'en-US,en;q=0.8'), ('Accept-Charset', 'ISO-8859-1,utf-8;q=0.7,*;q=0.3')] request = urllib2.Request(url, urlencode(data)) open("mycatpage.html", 'w').write(opener.open(request)) This has the same behavior...

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  • Python 2.7 list of lists manipulation functionality

    - by user3688163
    I am trying to perform several operations on the myList list of lists below and am having some trouble figuring it out. I am very new to Python. myList = [ ['Issue Id','1.Completeness for OTC','Break',3275,33,33725102303,296384802,20140107], ['Issue Id','2.Validity check1 for OTC','Break',3308,0,34021487105,0,20140107], ['Issue Id','3.Validity check2 for OTC','Break',3308,0,34021487105,0,20140107], ['Issue Id','4.Completeness for RST','Break',73376,1,8.24931E+11,44690130,20140107], ['Issue Id','5.Validity check1 for RST','Break',73377,0,8.24976E+11,0,20140107], ['Liquidity','1. OTC - Null','Break',7821 0,2.28291E+11,0,20140110], ['Liquidity','2. OTC - Unmapped','Break',7778,43,2.27712E+11,579021732.8,20140110], ['Liquidity','3. RST - Null','Break',335120,0,1.01425E+12,0,20140110], ['Liquidity','4. RST - Unmapped','Break',334608,512,1.01351E+12,735465433.1,20140110], ['Liquidity','5. RST - Valid','Break',335120,0,1.01425E+12,0,20140110], ['Issue Id','1.Completeness for OTC','Break',3292,33,32397924450,306203929,20140110], ['Issue Id','2.Validity check1 for OTC','Break',3325,0,32704128379,0,20140110], ['Issue Id','3.Validity check2 for OTC','Break',3325,0,32704128379,0,20140110], ['Issue Id','4.Completeness for RST','Break',73594,3,8.5352E+11,69614602,20140110], ['Issue Id','5.Validity check1 for RST','Break',73597,0,8.5359E+11,0,20140110], ['Unlinked Silver ID','DQ','Break',3201318,176,20000000,54974.33386,20140101], ['Missing GCI','DQ','Break',3201336,158,68000000,49351.9588,20140101], ['Missing Book','DQ Break',3192720,8774,3001000000,2740595.484,20140101], ['Matured Trades','DQ','Break',3201006,488,1371000000,152428.8348,20140101], ['Illiquid Trades','1.Completeness Check for range','Break',43122,47,88597695671,54399061.43,20140107], ['Illiquid Trades','2.Completeness Check for non','Break',39033,0,79133622401,0,20140107] ] I am trying to get the result below but do not know how to do so: newList = [ ['Issue Id','1.Completeness for OTC:2.Validity check1 for OTC:3.Validity check2 for OTC','Break',3275,33,33725102303,296384802,20140107], ['Issue Id','4.Completeness for RST:5.Validity check1 for RST','Break',73376,1,8.24931E+11,44690130,20140107], ['Liquidity','1. OTC - Null','Break:2. OTC - Unmapped','Break',7821 0,2.28291E+11,0,20140110], ['Liquidity','3. RST - Null:4. RST - Unmapped:5. RST - Valid','Break',335120,0,1.01425E+12,0,20140110], ['Issue Id','1.Completeness for OTC:2.Validity check1 for OTC:3.Validity check2 for OTC','Break',3292,33,32397924450,306203929,20140110], ['Issue Id','4.Completeness for RST:5. RST - Valid','Break',73594,3,8.5352E+11,69614602,20140110], ['Unlinked Silver ID','DQ','Break',3201318,176,20000000,54974.33386,20140101], ['Missing GCI','DQ','Break',3201336,158,68000000,49351.9588,20140101], ['Missing Book','DQ Break',3192720,8774,3001000000,2740595.484,20140101], ['Matured Trades','DQ','Break',3201006,488,1371000000,152428.8348,20140101], ['Illiquid Trades','1.Completeness Check for range','Break',43122,47,88597695671,54399061.43,20140107], ['Illiquid Trades','2.Completeness Check for non','Break',39033,0,79133622401,0,20140107] ] Rules to create newList. Create a new list in the newList list of lists if the values in the lists meet the following conditions: multiple lists that match on `myList[i][0]` and `myList[i][7]` but with have (1) sums of `myList[i][3]` and `myList[i][4]` and (2) sums of `myList[i][5]` and `myList[i][6]` that are different from each other are just listed as is in newList if multiple lists match on both `myList[i][0]` (this is the type) and `myList[i][7]` (this is the date) are the same then create a new list for each set of lists with mathcing `myList[i][0]` and `myList[i][7]` that have (1) sums of `myList[i][3]` and `myList[i][4]` and (2) sums of `myList[i][5]` and `myList[i][6]` that are different from the other lists with mathcing `myList[i][0]` and `myList[i][7]`. I also am trying to concatenate `myList[i][1]` separated by a ':' for all those lists with matching `myList[i][0]` and `myList[i][7]` and with sums of `myList[i][3]` + `myList[i][4]` and `myList[i][5]` + `myList[i][6]` that match. So essentially for this case only those lists in `myList` with sums of `myList[i][3]` + `myList[i][4]` and `myList[i][5]` + `myList[i][6]` are different from the other lists are then listed in newList. The above newList illustrates these results I am trying to achieve. If anyone has any ideas how to do this they would be greatly appreciated. Thank you!

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  • Trac FastCGI + Python on dreamhost leaves zombie python running

    - by Katsuke
    Hello there, Recently I installed trac in one of my dreamhost domains. I followed the instructions of http://trac.mlalonde.net/wiki/CreamyTrac and everything worked perfectly. At least i thought that was the case. After a few days, i started to notice that i was getting random 500 pages. I quickly checked the error log, and found a bunch of: [Fri Apr 16 14:35:34 2010] [error] [client *.*.*.*] Premature end of script headers: dispatch.fcgi [Fri Apr 16 14:35:54 2010] [error] [client *.*.*.*] Premature end of script headers: dispatch.fcgi, referer: http://www.trac.****.com/login [Fri Apr 16 16:05:58 2010] [error] [client *.*.*.*] Premature end of script headers: dispatch.fcgi, referer: http://www.trac.****.com/timeline The trac instance has very low traffic so it is possible that this might have been triggered faster if there was more use of it. So next step i went to look at top and am amazed by what i see: (this is NOT exactly what i saw, i just reproduced this from memory) 23730 rl_inst 20 0 44516 15m 4012 S 0.0 0.4 0:00.17 python2.4 23731 rl_inst 20 0 44616 15m 4012 S 0.0 0.4 0:03.17 python2.4 23732 rl_inst 20 0 44116 15m 4012 S 0.0 0.4 0:01.17 python2.4 23733 rl_inst 20 0 44826 15m 4012 S 0.0 0.4 0:04.17 python2.4 23734 rl_inst 20 0 44216 15m 4012 S 0.0 0.4 0:02.17 python2.4 23735 rl_inst 20 0 44416 15m 4012 S 0.0 0.4 0:01.17 python2.4 I opened the trac site again and that changed to this: 23730 rl_inst 20 0 44516 15m 4012 S 0.0 0.4 0:00.17 python2.4 23731 rl_inst 20 0 44616 15m 4012 S 0.0 0.4 0:03.17 python2.4 23732 rl_inst 20 0 44116 15m 4012 S 0.0 0.4 0:01.17 python2.4 23733 rl_inst 20 0 44826 15m 4012 S 0.0 0.4 0:04.17 python2.4 23734 rl_inst 20 0 44216 15m 4012 S 0.0 0.4 0:02.17 python2.4 23735 rl_inst 20 0 44416 15m 4012 S 0.0 0.4 0:01.17 python2.4 28378 rl_inst 20 0 2608 1208 1008 S 0.0 0.0 0:00.00 dispatch.fcgi 28382 rl_inst 20 0 44248 15m 4012 S 0.0 0.4 0:02.19 python2.4 So the dispatch.fcgi was being called correctly and was spawning correctly other python2.4 process. After the IDLE time passed this is the results: 23730 rl_inst 20 0 44516 15m 4012 S 0.0 0.4 0:00.17 python2.4 23731 rl_inst 20 0 44616 15m 4012 S 0.0 0.4 0:03.17 python2.4 23732 rl_inst 20 0 44116 15m 4012 S 0.0 0.4 0:01.17 python2.4 23733 rl_inst 20 0 44826 15m 4012 S 0.0 0.4 0:04.17 python2.4 23734 rl_inst 20 0 44216 15m 4012 S 0.0 0.4 0:02.17 python2.4 23735 rl_inst 20 0 44416 15m 4012 S 0.0 0.4 0:01.17 python2.4 28382 rl_inst 20 0 44248 15m 4012 S 0.0 0.4 0:02.19 python2.4 dispatch.fcgi was gone but the corresponding python2.4 was still there o_O. I had started with 5 sleeping processes of python and after idle time i ended up with 6. I repeated this and found that it kept spawning more and more python2.4, this was indeed what was causing my 500s indirectly. Let me explain my findings. Am on a shared hosting so my processes get killed if they are way too many. So everytime i opened trac 2 new processes spawned and one remained, to the point that dreamhost was killing a random process when i reached my limit. Sometimes killing the python2.4 that actually was rendering the current page. Hence header premature ending, python is gone the .fcgi doesnt know what to do and throws an 500. I found a dirty solution to this. I changed my dispatch.fcgi to contain a line that killed any currently running python2.4 process and then spawn a new one. Since then i dont get any rogues what so ever. But i dont think this is the best solution, calling killall in every fcgi just seems wrong. Anyone has run into this issue and found a cleaner solution? Is there anything that i have overlooked?

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  • How to set up Mod_WSGI for Python on Ubuntu

    - by AutomatedTester
    Hi, I am trying to setup MOD_WSGI on my Ubuntu box. I have found steps that said I needed to do the following steps I found at http://ubuntuforums.org/showthread.php?t=833766 sudo apt-get install libapache2-mod-wsgi sudo a2enmod mod-wsgi sudo /etc/init.d/apache2 restart sudo gedit /etc/apache2/sites-available/default and update the Directory <Directory /var/www/> Options Indexes FollowSymLinks MultiViews ExecCGI AddHandler cgi-script .cgi AddHandler wsgi-script .wsgi AllowOverride None Order allow,deny allow from all </Directory> sudo /etc/init.d/apache2 restart Created test.wsgi with def application(environ, start_response): status = '200 OK' output = 'Hello World!' response_headers = [('Content-type', 'text/plain'), ('Content-Length', str(len(output)))] start_response(status, response_headers) return [output] Step 2 fails because it says it can't find mod-wsgi even though the apt-get found it. If I carry on with the steps the python app just shows as plain text in a browser. Any ideas what I have done wrong? EDIT: Results for questions asked automatedtester@ubuntu:~$ dpkg -l libapache2-mod-wsgi Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) ||/ Name Version Description +++-======================================-======================================-============================================================================================ ii libapache2-mod-wsgi 2.5-1 Python WSGI adapter module for Apache automatedtester@ubuntu:~$ dpkg -s libapache2-mod-wsgi Package: libapache2-mod-wsgi Status: install ok installed Priority: optional Section: python Installed-Size: 376 Maintainer: Ubuntu MOTU Developers <[email protected]> Architecture: i386 Source: mod-wsgi Version: 2.5-1 Depends: apache2, apache2.2-common, libc6 (>= 2.4), libpython2.6 (>= 2.6), python (>= 2.5), python (<< 2.7) Suggests: apache2-mpm-worker | apache2-mpm-event Conffiles: /etc/apache2/mods-available/wsgi.load 06d2b4d2c95b28720f324bd650b7cbd6 /etc/apache2/mods-available/wsgi.conf 408487581dfe024e8475d2fbf993a15c Description: Python WSGI adapter module for Apache The mod_wsgi adapter is an Apache module that provides a WSGI (Web Server Gateway Interface, a standard interface between web server software and web applications written in Python) compliant interface for hosting Python based web applications within Apache. The adapter provides significantly better performance than using existing WSGI adapters for mod_python or CGI. Original-Maintainer: Debian Python Modules Team <[email protected]> Homepage: http://www.modwsgi.org/ automatedtester@ubuntu:~$ sudo a2enmod libapache2-mod-wsgi ERROR: Module libapache2-mod-wsgi does not exist! automatedtester@ubuntu:~$ sudo a2enmod mod-wsgi ERROR: Module mod-wsgi does not exist! FURTHER EDIT FOR RMYates automatedtester@ubuntu:~$ apache2ctl -t -D DUMP_MODULES apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName Loaded Modules: core_module (static) log_config_module (static) logio_module (static) mpm_worker_module (static) http_module (static) so_module (static) alias_module (shared) auth_basic_module (shared) authn_file_module (shared) authz_default_module (shared) authz_groupfile_module (shared) authz_host_module (shared) authz_user_module (shared) autoindex_module (shared) cgid_module (shared) deflate_module (shared) dir_module (shared) env_module (shared) mime_module (shared) negotiation_module (shared) python_module (shared) setenvif_module (shared) status_module (shared) Syntax OK automatedtester@ubuntu:~$

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