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  • fastest way to search through this data object? (python)

    - by victor
    I have a data object that looks like this: { 'node-16': { 'tags': ['cuda'], 'localNodes': [ { 'name': 'nC', 'consumesFrom': ['nA', 'nB'], 'classType': 'VectorAdder.VectorAdder' }, { 'name': 'nB', 'consumesFrom': None, 'classType': 'RandomVector' } ] }, 'node-17': { 'tags': ['boring'], 'localNodes': [ { 'name': 'nA', 'consumesFrom': None, 'classType': 'RandomVector' } ] } } Notice that node nA is a producer for nC. What's the fastest way to find out if a given localNode is a producer for another localnode in the data structure (and not within the same list)? For example, I would like to know that nA (node-17) produces for nC (exists on node-16). But I don't need to know that nB produces for nC, since they exist in the same localNodes list.

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  • Get class of caller's method (via inspect) in Python; or: super(Class,self).method() replacement wit

    - by Slava Vishnyakov
    Is it possible to get reference to class B in this example? class A(object): pass class B(A): def test(self): test2() class C(B): pass import inspect def test2(): frame = inspect.currentframe().f_back cls = frame.[?something here?] # cls here should == B (class) c = C() c.test() Basically, C is child of B, B is child of A. Then we create c of type C. Then the call to c.test() actually calls B.test() (via inheritance), which calls to test2(). test2() can get the parent frame frame; code reference to method via frame.f_code; self via frame.f_locals['self']; but type(frame.f_locals['self']) is C (of course), but not B, where method is defined. Any way to get B?

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  • python: a way to get an exhaustive, sorted list of keys in a nested dictionary?

    - by saidimu
    exhaustive: - all keys in the dictionary, even if the keys are in a nested dictionary that is a value to a previous-level dictionary key. sorted: - this is to ensure the keys are always returned in the same order The nesting is arbitrarily deep. A non-recursive algorithm is preferred. level1 = { 'a' : 'aaaa', 'level2_1' : {'b': 'bbbbb', 'level3': {'c': 'cccc', 'd': 'dddddd'} }, 'level2_2' : { 'z': 'zzzzzzz' } }

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  • Python: Find X to Y in a list of strings.

    - by TheLizardKing
    I have a list of maybe a 100 or so elements that is actually an email with each line as an element. The list is slightly variable because lines that have a \n in them are put in a separate element so I can't simply slice using fixed values. I essentially need a variable start and stop phrase (needs to be a partial search as well because one of my start phrases might actually be Total Cost: $13.43 so I would just use Total Cost:.) Same thing with the end phrase. I also do not wish to include the start/stop phrases in the returned list. In summary: email = ['apples','bananas','cats','dogs','elephants','fish','gee'] start = 'ban' stop = 'ele' the magic here new_email = ['cats','dogs'] NOTES While not perfect formatting of the email, it is fairly consistent so there is a slim chance a start/stop phrase will occur more than once. There are also no blank elements.

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  • Possible to capture the returned value from a Python list comprehension for use a condition?

    - by Joe
    I want to construct a value in a list comprehension, but also filter on that value. For example: [expensive_function(x) for x in generator where expensive_function(x) < 5] I want to avoid calling expensive_function twice per iteration. The generator may return an infinite series, and list comprehensions aren't lazily evaluated. So this wouldn't work: [y in [expensive_function(x) for x in generator where expensive_function(x)] where y < 5] I could write this another way, but it feels right for a list comprehension and I'm sure this is a common usage pattern (possible or not!).

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  • What's the life-time of a thread-local value in Python?

    - by Carlos Valiente
    import threading mydata = threading.local() def run(): # When will the garbage collector be able to destroy the object created # here? After the thread exits from ``run()``? After ``join()`` is called? # Or will it survive the thread in which it was created, and live until # ``mydata`` is garbage-collected? mydata.foo = object() t = threading.Thread(target=run) t.start() t.join()

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  • What are the elegant ways to do MixIns in Python?

    - by Slava Vishnyakov
    I need to find an elegant way to do 2 kinds of MixIns. First: class A(object): def method1(self): do_something() Now, a MixInClass should make method1 do this: do_other() - A.method1() - do_smth_else() - i.e. basically "wrap" the older function. I'm pretty sure there must exist a good solution to this. Second: class B(object): def method1(self): do_something() do_more() In this case, I want MixInClass2 to be able to inject itself between do_something() and do_more(), i.e.: do_something() - MixIn.method1 - do_more(). I understand that probably this would require modifying class B - that's ok, just looking for simplest ways to achieve this. These are pretty trivial problems and I actually solved them, but my solution is tainted. Fisrt one by using self._old_method1 = self.method1(); self.method1() = self._new_method1(); and writing _new_method1() that calls to _old_method1(). Problem: multiple MixIns will all rename to _old_method1 and it is inelegant. Second MixIn one was solved by creating a dummy method call_mixin(self): pass and injecting it between calls and defining self.call_mixin(). Again inelegant and will break on multiple MixIns.. Any ideas?

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  • Is it possible to use 'else' in a python list comprehension?

    - by Josh
    Here is the code I was trying to turn into a list comprehension: table = '' for index in xrange(256): if index in ords_to_keep: table += chr(index) else: table += replace_with Is there a way to add the else statement to this comprehension? table = ''.join(chr(index) for index in xrange(15) if index in ords_to_keep) Also, would I be right in concluding that a list comprehension is the most efficient way to do this?

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  • Python appengine Query does not work when using a variable.

    - by Lloyd
    Hi, I am trying to use a fetcher method to retrieve items from my datastore. If I use the following def getItem(item_id): q = Item.all() q.filter("itemid = ", item_id) It fails because nothing is returned. If I hard code in an item like def getItem(item_id): q = Item.all() q.filter("itemid = ", 9000) it fetches just fine, and sings merrily along. I have tried every which way to get this to work. I have used result = db.GqlQuery("SELECT * FROM Item WHERE item_id = :1 LIMIT 1", title).fetch(1) to the same effect. If I hard code in a number, works fine. I have tried setting the select statement as a local string, assembling it that way, casting the int as a string, and nothing. When I output the SELECT statement to the screen, looks fine. I can cut ans paste the output into the string, and whammo, it works. Any help would be appreciated.

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  • how to use @ in python.. and the @property and the @classmethods

    - by zjm1126
    this is my code: def a(): print 'sss' @a() def b(): print 'aaa' b() and the Traceback is: sss Traceback (most recent call last): File "D:\zjm_code\a.py", line 8, in <module> @a() TypeError: 'NoneType' object is not callable so how to use the '@' thanks updated class a: @property def b(x): print 'sss' aa=a() print aa.b it print : sss None how to use @property thanks updated2 and the classmethods: class a: @classmethods def b(x): print 'sss' aa=a() print aa.b the Traceback is : Traceback (most recent call last): File "D:\zjm_code\a.py", line 5, in <module> class a: File "D:\zjm_code\a.py", line 6, in a @classmethods NameError: name 'classmethods' is not defined

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  • Python instances and attributes: is this a bug or i got it totally wrong?

    - by Mirko Rossini
    Suppose you have something like this: class intlist: def __init__(self,l = []): self.l = l def add(self,a): self.l.append(a) def appender(a): obj = intlist() obj.add(a) print obj.l if __name__ == "__main__": for i in range(5): appender(i) A function creates an instance of intlist and calls on this fresh instance the method append on the instance attribute l. How comes the output of this code is: [0] [0, 1] [0, 1, 2] [0, 1, 2, 3] [0, 1, 2, 3, 4] ? If i switch obj = intlist() with obj = intlist(l=[]) I get the desired output [0] [1] [2] [3] [4] Why this happens? Thanks

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  • Build a decision tree for classification of large amount data,using python?

    - by kaushik
    Hi,i am working for speech synthesis.In this i have a large number of pronunciation for each phone i.e alphabet and need to classify them according to few feature such as segment size(int) and alphabet itself(string) into a smaller set suitable for that particular context. For this purpose,i have decided to use decision tree for classification.the data to be parsed is in the S expression format.eg:((question)(LEFTNODE)(RIGHTNODE)). i hav idea for building decision tree for normal buit in type such as list..looking for suggestion for implementation for S expression.. kindly help.. Thanks in advance.. Note:this question may look similar to my prev post,srry if cant giv multiple post.already edited it many times so though of wirting new question instead of editing again

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  • So, I guess I can't use "&&" in the Python if conditional. Any help?

    - by Sergio Tapia
    Here's my code: # F. front_back # Consider dividing a string into two halves. # If the length is even, the front and back halves are the same length. # If the length is odd, we'll say that the extra char goes in the front half. # e.g. 'abcde', the front half is 'abc', the back half 'de'. # Given 2 strings, a and b, return a string of the form # a-front + b-front + a-back + b-back def front_back(a, b): # +++your code here+++ if len(a) % 2 == 0 && len(b) % 2 == 0: return a[:(len(a)/2)] + b[:(len(b)/2)] + a[(len(a)/2):] + b[(len(b)/2):] else: #todo! Not yet done. :P return I'm getting an error in the IF conditional. What am I doing wrong?

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