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• How do you check the presence of many keys in a Python dictinary?

  - by Thierry Lam

  I have the following dictionary: sites = { 'stackoverflow': 1, 'superuser': 2, 'meta': 3, 'serverfault': 4, 'mathoverflow': 5 } To check if there are more than one key available in the above dictionary, I will do something like: 'stackoverflow' in sites and 'serverfault' in sites The above is maintainable with only 2 key lookups. Is there a better way to handle checking a large number of keys in a very big dictionary?

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• Add characters (',') every time a certain character ( , )is encountered ? Python 2.7.3

  - by draconisthe0ry

  Let's say you had a string test = 'wow, hello, how, are, you, doing' and you wanted full_list = ['wow','hello','how','are','you','doing'] i know you would start out with an empty list: empty_list = [] and would create a for loop to append the items into a list i'm just confused on how to go about this, I was trying something along the lines of: for i in test: if i == ',': then I get stuck . . .

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• how to write or create(when no exist) a file using python..

  - by zjm1126

  this is my code: f = open('text/a.log', 'wb') f.write('hahaha') f.close() and it is not create a new file when not exist how to do this , thanks

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• How can I use python itertools.groupby() to group a list of strings by their first character?

  - by Adam Z.

  I have a list of strings similar to this list: tags = ('apples', 'apricots', 'oranges', 'pears', 'peaches') How should I go about grouping this list by the first character in each string using itertools.groupby()? How should I supply the 'key' argument required by itertools.groupby()?

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• Is there a better way to format this Python/Django code as valid PEP8?

  - by Ryan Detzel

  I have code written both ways and I see flaws in both of them. Is there another way to write this or is one approach more "correct" than the other? def functionOne(subscriber): try: results = MyModelObject.objects.filter( project__id=1, status=MyModelObject.STATUS.accepted, subscriber=subscriber).values_list( 'project_id', flat=True).order_by('-created_on') except: pass def functionOne(subscriber): try: results = MyModelObject.objects.filter( project__id=1, status=MyModelObject.STATUS.accepted, subscriber=subscriber) results = results.values_list('project_id', flat=True) results = results.order_by('-created_on') except: pass

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• How to make if-elif-else statement in python more space-saving?

  - by Neverland

  I have a lot of if-elif-else statements in my code if message == '0' or message == '3' or message == '5' or message == '7': ... elif message == '1' or message == '2' or message == '4' or message == '6' or message == '8': ... else: ... Is it possible to format this in a more space-saving way? I tried it this way: if message == '0' or '3' or '5' or '7': ... elif message == '1' or '2' or '4' or '6' or '8': ... else: ... But without success.

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• Elegent way to collapse or expand sub-sequences of a list in Python?

  - by forgot

  I want to collapse or expand sub-sequences of a list e.g. ['A', 'B', 'D', 'E', 'H'] -> ['AB', 'DE', 'H'] and vice versa currently I wrote some ugly code like: while True: for i, x in enumerate(s): if x == 'A' and s[i+1] == 'B': s[i:i+2] = 'AB' break else: break For people who asking 'why do that thing': Actually I'm working on a optimizing compiler and this is the peephole part. Writing pattern matching is a little annoying.

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• between C# and Python, which is better at random number generation?

  - by Matt

  Without relying on third party libraries or obscenely complex custom number generating things, which of those two languages makes the most 'random' random numbers? not too important, just a program that simulates dice rolls (I'm still a little new at both languages)

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• Can a python view template be made to be 'safe/secure' if I make it user editable?

  - by Blankman

  Say I need to have a templating system where a user can edit it online using an online editor. So they can put if tags, looping tags etc., but ONLY for specific objects that I want to inject into the template. Can this be made to be safe from security issues? i.e. them somehow outputing sql connection string information or scripting things outside of the allowable tags and injected objects.

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• Python: Is there a way to split a string of numbers into every 3rd number?

  - by Kyle W

  For example, if I have a string a=123456789876567543 could i have a list like... 123 456 789 876 567 543

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• What is the difference between a module and a script in Python?

  - by Shailesh Tainwala

  Think the title summarizes the question :-)

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• What scales better? Ruby or Python? [closed]

  - by Marco

  Which language would be easier to scale? We are not using a framework.

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• In Python, are there builtin functions for elementwise boolean operators over boolean lists?

  - by bshanks

  For example, if you have n lists of bools of the same length, then elementwise boolean AND should return another list of that length that has True in those positions where all the input lists have True, and False everywhere else. It's pretty easy to write, i just would prefer to use a builtin if one exists (for the sake of standardization/readability). Here's an implementation of elementwise AND: def eAnd(*args): return [all(tuple) for tuple in zip(*args)] example usage: >>> eAnd([True, False, True, False, True], [True, True, False, False, True], [True, True, False, False, True]) [True, False, False, False, True] thx

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• List in a Python class shares the same object over 2 different instances?

  - by zfranciscus

  I created a class: class A: aList = [] now I have function that instantiate this class and add items into the aList. note: there are 2 items for item in items: a = A(); a.aList.append(item); I find that the first A and the second A object has the same number of items in their aList. I would expect that the first A object will have the first item in its list and the second A object will have the second item in its aList. Can anyone explain how this happens ? PS: I manage to solve this problem by moving the aList inside a constructor : def __init__(self): self.aList = []; but I am still curious about this behavior

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• how to get the parent dir location using python..

  - by zjm1126

  this code is get the templates/blog1/page.html in b.py: path = os.path.join(os.path.dirname(__file__), os.path.join('templates', 'blog1/page.html')) but i want to get the parent dir location: a |---b.py |---templates |--------blog1 |-------page.html and how to get the a location thanks

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• How to add values accordingly of the first indices of a dictionary of tuples of a list of strings? Python 3x

  - by TheStruggler

  I'm stuck on how to formulate this problem properly and the following is: What if we had the following values: {('A','B','C','D'):3, ('A','C','B','D'):2, ('B','D','C','A'):4, ('D','C','B','A'):3, ('C','B','A','D'):1, ('C','D','A','B'):1} When we sum up the first place values: [5,4,2,3] (5 people picked for A first, 4 people picked for B first, and so on like A = 5, B = 4, C = 2, D = 3) The maximum values for any alphabet is 5, which isn't a majority (5/14 is less than half), where 14 is the sum of total values. So we remove the alphabet with the fewest first place picks. Which in this case is C. I want to return a dictionary where {'A':5, 'B':4, 'C':2, 'D':3} without importing anything. This is my work: def popular(letter): '''(dict of {tuple of (str, str, str, str): int}) -> dict of {str:int} ''' my_dictionary = {} counter = 0 for (alphabet, picks) in letter.items(): if (alphabet[0]): my_dictionary[alphabet[0]] = picks else: my_dictionary[alphabet[0]] = counter return my_dictionary This returns duplicate of keys which I cannot get rid of. Thanks.

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• Why are these strings escaping from my regular expression in python?

  - by dohkoxar

  In my code, I load up an entire folder into a list and then try to get rid of every file in the list except the .mp3 files. import os import re path = '/home/user/mp3/' dirList = os.listdir(path) dirList.sort() i = 0 for names in dirList: match = re.search(r'\.mp3', names) if match: i = i+1 else: dirList.remove(names) print dirList print i After I run the file, the code does get rid of some files in the list but keeps these two especifically: ['00. Various Artists - Indie Rock Playlist October 2008.m3u', '00. Various Artists - Indie Rock Playlist October 2008.pls'] I can't understand what's going on, why are those two specifically escaping my search.

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• why can't I use "&&" in python to mean 'and'?

  - 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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• I'm doing a lot of lists and dictionary sorting...and this is causing memory errors in Python websit

  - by alex

  I retrieved data from the log table in my database. Then I started finding unique users, comparing/sorting lists, etc. In the end I got down to this. stats = {'2010-03-19': {'date': '2010-03-19', 'unique_users': 312, 'queries': 1465}, '2010-03-18': {'date': '2010-03-18', 'unique_users': 329, 'queries': 1659}, '2010-03-17': {'date': '2010-03-17', 'unique_users': 379, 'queries': 1845}, '2010-03-16': {'date': '2010-03-16', 'unique_users': 434, 'queries': 2336}, '2010-03-15': {'date': '2010-03-15', 'unique_users': 390, 'queries': 2138}, '2010-03-14': {'date': '2010-03-14', 'unique_users': 460, 'queries': 2221}, '2010-03-13': {'date': '2010-03-13', 'unique_users': 507, 'queries': 2242}, '2010-03-12': {'date': '2010-03-12', 'unique_users': 629, 'queries': 3523}, '2010-03-11': {'date': '2010-03-11', 'unique_users': 811, 'queries': 4274}, '2010-03-10': {'date': '2010-03-10', 'unique_users': 171, 'queries': 1297}, '2010-03-26': {'date': '2010-03-26', 'unique_users': 299, 'queries': 1617}, '2010-03-27': {'date': '2010-03-27', 'unique_users': 323, 'queries': 1310}, '2010-03-24': {'date': '2010-03-24', 'unique_users': 352, 'queries': 2112}, '2010-03-25': {'date': '2010-03-25', 'unique_users': 330, 'queries': 1290}, '2010-03-22': {'date': '2010-03-22', 'unique_users': 329, 'queries': 1798}, '2010-03-23': {'date': '2010-03-23', 'unique_users': 329, 'queries': 1857}, '2010-03-20': {'date': '2010-03-20', 'unique_users': 368, 'queries': 1693}, '2010-03-21': {'date': '2010-03-21', 'unique_users': 329, 'queries': 1511}, '2010-03-29': {'date': '2010-03-29', 'unique_users': 325, 'queries': 1718}, '2010-03-28': {'date': '2010-03-28', 'unique_users': 340, 'queries': 1815}, '2010-03-30': {'date': '2010-03-30', 'unique_users': 329, 'queries': 1891}} It's not a big dictionary. But when I try to do one last thing...it craps out on me. for k, v in stats: mylist.append(v) too many values to unpack What the heck does that mean??? TOO MANY VALUES TO UNPACK.

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• How to get latest facebook status update in python?

  - by Peter

  I need to be able to get the latest facebook status update of an user that has allowed consent. Is there a way to do this with pyfacebook without having to have the user login in facebook?

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• Is there a memory efficient and fast way to load big json files in python?

  - by user210481

  I have some json files with 500MB. If I use the "trivial" json.load to load its content all at once, it will consume a lot of memory. Is there a way to read partially the file? If it was a text, line delimited file, I would be able to iterate over the lines. I am looking for analogy to it. Any suggestions? Thanks

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• Python - Is it possible to get the name of the chained function?

  - by user1326876

  I'm working on a class that basically allows for method chaining, for setting some attrbutes for different dictionaries stored. The syntax is as follows: d = Test() d.connect().setAttrbutes(Message=Blah, Circle=True, Key=True) But there can also be other instances, so, for example: d = Test() d.initialise().setAttrbutes(Message=Blah) Now I believe that I can overwrite the "setattrbutes" function; I just don't want to create a function for each of the dictionary. Instead I want to capture the name of the previous chained function. So in the example above I would then be given "connect" and "initialise" so I know which dictionary to store these inside. I hope this makes sense. Any ideas would be greatly appreciated :)

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• Why are python extensions shared libraries? Is it possible to make a static-linked library?

  - by Andrew Moffat

  I'm an extension noob. What I want to do is create an extension that doesn't require other libraries to be installed. Is this impossible because the extension has to link against a specific version of libpython at runtime?

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• Geometry library for python (or C++) for CAD-like operations?

  - by gct

  I'm trying to put together a simple program that will let me visualize a series of consecutive cuts on a wood panel using a router with a particular cutting head. I'm trying to find a decent geometry library that will give me a shortcut through the CAD-like stuff. Specifically, I'd like to be able to define a rectangular solid (the wood panel) and then define a bit profile shape, and take cuts through the rectangular solid (sometimes on a straight line, sometimes on a circular arc). Does anyone know of anything that will do this?

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• Would Python's Twisted library be the best case for an observer type pattern?

  - by beagleguy

  hi all, I'm developing a system where a queue will be filled with millions of items I need a process that reads items from the queue constantly and then sends those items out to registered clients. I'm thinking about using twisted for this, having the queue reader be a twisted server listening on a tcp port then clients can connect on that port and when an item is pulled from the queue the server writes it out to all the clients. Does that sound like something that twisted would be ideal for? Does anyone know of any sample code out there that may do something similar? thanks

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