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• Comparing (similar) images with Python/PIL

  - by Attila Oláh

  I'm trying to calculate the similarity (read: Levenshtein distance) of two images, using Python 2.6 and PIL. I plan to use the python-levenshtein library for fast comparison. Main question: What is a good strategy for comparing images? My idea is something like: Convert to RGB (transparent - white) (or maybe convert to monochrome?) Scale up the smaller one to the larger one's size Convert each channel (= the only channel, if converted to monochrome) to a sequence (item value = color value of the pixel) Calculate the Levenshtein distance between the two sequences Of course, this will not handle cases like mirrored images, cropped images, etc. But for basic comparison, this should be useful. Is there a better strategy documented somewhere?

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• Writing to a new line of a file in Objective-C

  - by Kulpreet

  For some strange reason, the \n and \r escape sequences do not seem to be working in my code. I want to write each NSString on a new line of the file, but it just appends it the last string on one line. Here's the code: for (Entry *entry in self.entries) { NSString *path = @"/Users/me/File.txt"; NSString *string = (@"%@\r\n", [entry thisEntry]); NSFileHandle *fh = [NSFileHandle fileHandleForWritingAtPath:path]; [fh seekToEndOfFile]; [fh writeData:[string dataUsingEncoding:NSUnicodeStringEncoding]]; [fh closeFile]; } Am I doing something wrong? Forgive me as I am new to Objective-C.

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• Deriving arrays in mathematics

  - by Gio Borje

  So I found some similarities between arrays and set notation while learning about sets and sequences in precalc e.g. set notation: {a | cond } = { a1, a2, a3, a4, ..., an} given that n is the domain (or index) of the array, a subset of Natural numbers (or unsigned integer). Most programming languages would provide similar methods to arrays that are applied to sets e.g. upperbounds & lowerbounds; possibly suprema and infima too. Where did arrays come from?

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• BioPython: extracting sequence IDs from a Blast output file

  - by Jon

  Hi, I have a BLAST output file in XML format. It is 22 query sequences with 50 hits reported from each sequence. And I want to extract all the 50x22 hits. This is the code I currently have, but it only extracts the 50 hits from the first query. from Bio.Blast import NCBIXM blast_records = NCBIXML.parse(result_handle) blast_record = blast_records.next() save_file = open("/Users/jonbra/Desktop/my_fasta_seq.fasta", 'w') for alignment in blast_record.alignments: for hsp in alignment.hsps: save_file.write('>%s\n' % (alignment.title,)) save_file.close() Somebody have any suggestions as to extract all the hits? I guess I have to use something else than alignments. Hope this was clear. Thanks! Jon

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• convert string to float without silent NaN/Inf conversion

  - by Peter Hansen

  I'd like convert strings to floats using Python 2.6 and later, but without silently converting things like 'NaN' and 'Inf'. Before 2.6, float("NaN") would raise a ValueError. Now it returns a float for which math.isnan() returns True, which is not useful behaviour for my application. Here's what I've got at the moment: import math def get_floats(source): for text in source.split(): try: val = float(text) if math.isnan(val) or math.isinf(val): raise ValueError yield val except ValueError: pass This is a generator, which I can supply with strings containing whitespace-separated sequences representing real numbers. I'd like it to yield only those fields which are purely numeric representations of floats, as in "1.23" or "-34e6", but not for example "NaN" or "-Inf". Test case: assert list(get_floats('1.23 -34e6 NaN -Inf')) == [1.23, -34000000.0] Please suggest alternatives you consider more elegant, even if they involve "look before you leap" (which is normally considered a lesser approach in Python).

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• Is there something like "if not exist create sequence ..." in Oracle SQL?

  - by Timo

  Very probably a noob question: For my application that uses an Oracle 8 DB, I am providing an SQL script to setup stuff like triggers, sequences etc., which can be copied and pasted into SQL*Plus. I would like the script to not stop with an error if a sequence that I am trying to create already exists. For a Trigger this can easily be done using "create or replace trigger ...", but for a sequence this does not work. Is there some alternative, like "if not exists mysequence then create sequence ..." (I tried this but it did not work :) ) Alternatively, if this is not possible, is there a way to do a "drop sequence mysequence" without SQL*Plus aborting the script if mysequence does not exist? Thanks. PS: I wish Oracle just had a simple Autoinc field type ... sigh.

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• Sequence numbers best practice

  - by Abdullah Jibaly

  What's the best practice or well known methods to implement sequence numbers for business entities such as invoices, purchase orders, job numbers, etc? I want to be able to save the latest value in the database and be able to set it programatically. Is it OK to use a table for this purpose that has a SEQUENCE_NAME, SEQUENCE_NUMBER tuple? I know some databases have a first class sequence type but others (eg, MySQL) do not so it's not something I want to rely on. If a table is used to hold these sequences what is the right way to get and increment them in a synchronized fashion to ensure no data inconsistencies arise?

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• OpenCV in Python can't scan through pixels

  - by Marco L.

  Hi everyone, I'm stuck with a problem of the python wrapper for OpenCv. I have this function that returns 1 if the number of black pixels is greater than treshold def checkBlackPixels( img, threshold ): width = img.width height = img.height nchannels = img.nChannels step = img.widthStep dimtot = width * height data = img.imageData black = 0 for i in range( 0, height ): for j in range( 0, width ): r = data[i*step + j*nchannels + 0] g = data[i*step + j*nchannels + 1] b = data[i*step + j*nchannels + 2] if r == 0 and g == 0 and b == 0: black = black + 1 if black >= threshold * dimtot: return 1 else: return 0 The loop (scan each pixel of a given image) works good when the input is an RGB image...but if the input is a single channel image I get this error: for j in range( width ): TypeError: Nested sequences should have 2 or 3 dimensions The input single channel image (called 'rg' in the next example) is taken from an RGB image called 'src' processed with cvSplit and then cvAbsDiff cvSplit( src, r, g, b, 'NULL' ) rg = cvCreateImage( cvGetSize(src), src.depth, 1 ) # R - G cvAbsDiff( r, g, rg ) I've also already noticed that the problem comes from the difference image got from cvSplit... Anyone can help me? Thank you

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• split a string based on pattern in java - capital letters and numbers

  - by rookie

  Hi all I have the following string "3/4Ton". I want to split it as -- word[1] = 3/4 and word[2] = Ton. Right now my piece of code looks like this:- Pattern p = Pattern.compile("[A-Z]{1}[a-z]+"); Matcher m = p.matcher(line); while(m.find()){ System.out.println("The word --> "+m.group()); } It carries out the needed task of splitting the string based on capital letters like:- String = MachineryInput word[1] = Machinery , word[2] = Input The only problem is it does not preserve, numbers or abbreviations or sequences of capital letters which are not meant to be separate words. Could some one help me out with my regular expression coding problem. Thanks in advance...

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• Does any one know of a packet generator?

  - by Benoit

  We have a networked device, and we would like to perform some tests on how it handles malformed packets. Is there a product out there that can generate arbitrary packets and packet sequences? I would like to be able to specify a set of TCP/IP payloads and it would open a connection and send the data. Obviouly, the TCP/IP checksum should be calculated correctly, etc... Kind of like a wireshark in reverse. Note that I am not interested in network loading and blasting millions of packet.

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• Intra-Unicode "lean" Encoding Converters

  - by Mystagogue

  Windows provides encoding conversion functions ("MultiByteToWideChar" and "WideCharToMultiByte") which are capable of UTF-8 to/from UTF-16 conversions, among other things. But I've seen people offer home-grown 30 to 40 line functions that claim also to perform UTF-8 / UTF-16 encoding conversions. My question is, how reliable are such tiny converters? Can such a tiny amount of code handle problems such as converting a UTF-16 surrogate pair (such as ) into a UTF-8 single four byte sequence (rather than making the mistake of converting into a pair of three byte sequences)? Can they correctly spot "unpaired" surrogate input, and provide an error? In short, are such tiny converters mere toys, or can they be taken seriously? For that matter, why does unicode.org seemingly offer no advice on an algorithm for accomplishing such conversions?

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• problem with JMF !

  - by Razan

  Hi.. I have windows vista OS.. I Installed JMF to work with it.. but it seems I'm having some conflicts between Sound and JMF.. because after I installed JMF my projects that use Sound.. midi.. sequences.. are giving exceptions that they don't have some sound classes and so.. and when I removed JMF every thing went OK !! so what I'm gonna do?

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• Specifying distinct sequence per table in Hibernate on subclasses

  - by gutch

  Is there a way to specify distinct sequences for each table in Hibernate, if the ID is defined on a mapped superclass? All entities in our application extend a superclass called DataObject like this: @MappedSuperclass public abstract class DataObject implements Serializable { @Id @GeneratedValue(strategy = GenerationType.SEQUENCE) @Column(name = "id") private int id; } @Entity @Table(name = "entity_a") public class EntityA extends DataObject { ... } @Entity @Table(name = "entity_b") public class EntityB extends DataObject { ... } This causes all entities to use a shared sequence, the default hibernate_sequence. What I would like to do is use a separate sequence for each entity, for example entity_a_sequence and entity_b_sequence in the example above. If the ID were specified on the subclasses then I could use the @SequenceGenerator annotation to specify a sequence for each entity, but in this case the ID is on the superclass. Given that ID is in the superclass, is there a way I can use a separate sequence for each entity — and if so, how? (We are using PostgreSQL 8.3, in case that's relevant)

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• Most elegant way to morph this sequence

  - by Ed Woodcock

  Hi folks: I've got the Day of the week stored in a database table (that I do not control), and I need to use it in my code. Problem is, I want to use the System.DayOfWeek enum for representation for this, and the sequences are not the same. In the database, it's as follows: 1 2 3 4 5 6 7 S M T W T F S I need it as follows: 0 1 2 3 4 5 6 M T W T F S S What's the most elegant way to do this? for example, I could do: i = dayOfWeek; i = i - 2; if (i < 0) { i = 6; } but that's a bit inelegant. Any suggestions?

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• Encode/compress sequence of repeating integers

  - by Alex

  Hey there! I have very long integer sequences that look like this (arbitrary length!): 0000000001110002220033333 Now I need some algorithm to convert this string into something compressed like a9b3a3c3a2d5 Which means "a 9 times, then b 3 times, then a 3 times" and so on, where "a" stands for 0, "b" for 1, "c" for 2 and "d" for 3. How would you do that? So far nothing suitable came to my mind, and I had no luck with google because I didn't really know what to search for. What is this kind of encoding / compression called? PS: I am going to do the encoding with PHP, and the decoding in JavaScript.

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• What should I call a class that contains a sequence of states

  - by Robert P

  I have a GUI tool that manages state sequences. One component is a class that contains a set of states, your typical DFA state machine. For now, I'll call this a StateSet. However, I have another class that has a collection (possibly partially unordered) of those state sets, and lists them in a particular order. and I'm trying to come up with a good name for it - not just for internal code, but for customers to refer to it. I've got: Sequence (maybe) StateSetSet (reasonable for code, but not for customers) Any other suggestions or ideas?

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• Regular expression for parsing CSV in PHP

  - by Discodancer

  I already managed to split the CSV file using this regex: "/,(?=(?:[^\"]\"[^\"]\")(?![^\"]\"))/" But I ended up with an array of strings that contain the opening and ending double quotes. Now I need a regex that would strip those strings of the delimiter double quotes. As far as I know the CSV format can encapsulate strings in double quotes, and all the double quotes that are already a part of the string are doubled. For example: My "other" cat becomes "My ""other"" cat" What I basically need is a regex that will replace all sequences of N doublequotes with a sequence of (N/2 - rounded down) double quotes. Or is there a better way ? Thanks in advance.

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• MS SQL replace sequence of same characters inside Text Field (TSQL only)

  - by zmische

  I have a text column varchar(4000) with text: 'aaabbaaacbaaaccc' and I need to remove all duplicated chars - so only one from sequence left: 'abacbac' It should not be a function, Procedure or CLR - Regex solution. Only true SQL select. Currently I think about using recursive WITH clause with replace 'aa'-'a', 'bb'-'b', 'cc'-'c'. So recursion should cycle until all duplicated sequences of that chars would be replaced. DO you have another solution, perhaps more Permormant one? PS: I searched through this site about different replace examples - they didnt suit to this case.

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• Convert matched string of UTF-8 values to UTF-8 characters in Ruby

  - by user1475154

  Trying to convert output from a rest_client GET to the characters that are represented with escape sequences. Input: ..."sub_id":"\u0d9c\u8138\u8134\u3f30\u8139\u2b71"... (which I put in 'all_subs') Match: m = /sub_id\"\:\"([^\"]+)\"/.match(all_subs.to_str) [1] Print: puts m.force_encoding("UTF-8").unpack('U*').pack('U*') But it just comes out the same way I put it in. ie, "\u0d9c\u8138\u8134\u3f30\u8139\u2b71" However, if I convert a raw string of it: puts "\u0d9c\u8138\u8134\u3f30\u8139\u2b71".unpack('U*').pack('U*') The output is perfect as "??????"

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• Calculating probability that a string has been randomized? - Python

  - by RadiantHex

  Hi folks, this is correlated to a question I asked earlier (question) I have a list of manually created strings such as: lucy87 gordan_king fancy_unicorn77 joplucky_kanga90 base_belong_to_narwhals and a list of randomized strings: johnkdf pancake90kgjd fancy_jagookfk manhattanljg What gives away that the last set of strings are randomized is that sequences such as 'kjg', 'jgf', 'lkd', ... . Any clever way I could separate strings that contain these apparently randomized strings from the crowd? I guess that this plays a lot on the fact that certain characters are more likely to be placed next to others (e.g. 'co', 'ka', 'ja', ...). Any ideas on this one? Kylotan mentioned Reverend, but I am not sure if it can be used fr such purpose. Help would be much appreciated!

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• Should I convert overlong UTF-8 strings to their shortest normal form?

  - by Grant McLean

  I've just been reworking my Encoding::FixLatin Perl module to handle overlong UTF-8 byte sequences and convert them to the shortest normal form. My question is quite simply "is this a bad idea"? A number of sources (including this RFC) suggest that any over-long UTF-8 should be treated as an error and rejected. They caution against "naive implementations" and leave me with the impression that these things are inherently unsafe. Since the whole purpose of my module is to clean up messy data files with mixed encodings and convert them to nice clean utf8, this seems like just one more thing I can clean up so the application layer doesn't have to deal with it. My code does not concern itself with any semantic meaning the resulting characters might have, it simply converts them into a normalised form. Am I missing something. Is there a hidden danger I haven't considered?

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• Is OpenGL required for my iPhone game?

  - by Ben X Tan

  On an iPhone: If I am writing a game that has multiple levels, with multiple animations (image sequences), jpg and png (transparent), some full screen and some not, some looped and some played once only. What is the best way of doing it? Each level might have up to 10MB of images. Add on to this music, and video (cut scenes). All 2D graphics, no 3D models. Is OpenGL required? Or can this be achieved with Quartz or Core Animation?

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• Working with multiple input and output files in Python

  - by Morlock

  I need to open multiple files (2 input and 2 output files), do complex manipulations on the lines from input files and then append results at the end of 2 output files. I am currently using the following approach: in_1 = open(input_1) in_2 = open(input_2) out_1 = open(output_1, "w") out_2 = open(output_2, "w") # Read one line from each 'in_' file # Do many operations on the DNA sequences included in the input files # Append one line to each 'out_' file in_1.close() in_2.close() out_1.close() out_2.close() The files are huge (each potentially approaching 1Go, that is why I am reading through these input files one at a time. I am guessing that this is not a very Pythonic way to do things. :) Would using the following form good? with open("file1") as f1: with open("file2") as f2: # etc. If yes, could I do it while avoiding the highly indented code that would result? Thanks for the insights!

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• Operant conditioning algorithm?

  - by Ken

  What's the best way to implement real time operant conditioning (supervised reward/punishment-based learning) for an agent? Should I use a neural network (and what type)? Or something else? I want the agent to be able to be trained to follow commands like a dog. The commands would be in the form of gestures on a touchscreen. I want the agent to be able to be trained to follow a path (in continuous 2D space), make behavioral changes on command (modeled by FSM state transitions), and perform sequences of actions. The agent would be in a simulated physical environment.

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• Unicode and URI encoding, decoding and escaping in JavaScript

  - by apphacker

  If you look at this table here, it has a list of escape sequences for Unicode characters that don't actually work for me. For example for "%96", which should be a –, I get an error when trying decode: decodeURIComponent("%96"); URIError: URI malformed If I attempt to encode "–" I actually get: encodeURIComponent("–"); "%E2%80%93" I searched through the internet and I saw this page, which mentions using escape and unescape with decodeURIComponent and encodeURIComponent respectively. This doesn't seem to help because %96 doesn't show up as "–" no matter what I try and this of course wouldn't work: decodeURIComponent(escape("%96)); "%96" Not very helpful. How can I get "%96" to be a "–" with JavaScript (without hardcoding a map for every single possible unicode character I may run into)?

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