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• Is there a clever way to pass the key to defaultdict's default_factory?

  - by Paul Oyster

  A class has a constructor which takes one parameter: class C(object): def __init__(self, v): self.v = v ... Somewhere in the code, it is useful for values in a dict to know their keys. I want to use a defaultdict with the key passed to newborn default values: d = defaultdict(lambda : C(here_i_wish_the_key_to_be)) Any suggestions?

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• Django - count date between

  - by DJPy

  I have many record in my database wich contains datetime field (e.g. 2010-05-23 17:45:57). I want to count all records between e.g. 15:00 and 15:59 (it all can by from other day, month or year). How can I do this?

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• element-wise lookup on one ndarray to another ndarray of different shapes

  - by fahhean

  Hi, I am new to numpy. Am wonder is there a way to do lookup of two ndarray of different shapes? for example, i have 2 ndarrays as below: X = array([[0, 3, 6], [3, 3, 3], [6, 0, 3]]) Y = array([[0, 100], [3, 500], [6, 800]]) and would like to lookup each element of X in Y, then be able to return the second column of Y: Z = array([[100, 500, 800], [500, 500, 500], [800, 100, 500]]) thanks, fahhean

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• how to get all 'username' from my model 'MyUser' on google-app-engine ..

  - by zjm1126

  my model is : class MyUser(db.Model): user = db.UserProperty() password = db.StringProperty(default=UNUSABLE_PASSWORD) email = db.StringProperty() nickname = db.StringProperty(indexed=False) and my method which want to get all username is : s=[] a=MyUser.all().fetch(10000) for i in a: s.append(i.username) and the error is : AttributeError: 'MyUser' object has no attribute 'username' so how can i get all 'username', which is the simplest way . thanks

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• add new records using signal in django admin

  - by ganesh

  I've a model called broadcastinfo, It has fields viz.. info,userid...userid is excluded. when i add an new info, my broadcastinfo table should get the records of all userid from user table and the given message. Im trying this via signal.Any idea is highly appreciated. Thanks

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• Exception Handaling in google app engine

  - by Rahul99

  i am raising exception using if UserId == '' and Password == '': raise Exception.MyException , "wrong userId or password" but i want print the error message on same page class MyException(Exception): def __init__(self,msg): Exception.__init__(self,msg)

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• Is there any way to do this without using '__init__'?

  - by zjm1126

  class a(object): c=b()# how to call the b method d=4 def __init__(self): print self.c def b(self): return self.d+1 a() how to call the 'b' method not in the __init__ thanks the error is : Traceback (most recent call last): File "D:\zjm_code\a.py", line 12, in <module> class a(object): File "D:\zjm_code\a.py", line 13, in a c=b()# how to call the b method NameError: name 'b' is not defined

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• Is a string formatter that pulls variables from its calling scope bad practice?

  - by Eric

  I have some code that does an awful lot of string formatting, Often, I end up with code along the lines of: "...".format(x=x, y=y, z=z, foo=foo, ...) Where I'm trying to interpolate a large number of variables into a large string. Is there a good reason not to write a function like this that uses the inspect module to find variables to interpolate? import inspect def interpolate(s): return s.format(**inspect.currentframe().f_back.f_locals) def generateTheString(x): y = foo(x) z = x + y # more calculations go here return interpolate("{x}, {y}, {z}")

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• A Tkinter StringVar() Question

  - by Graham

  I would like to create a StringVar() that looks something like this: someText = "The Spanish Inquisition" #Here's a normal variable whose value I will change eventually TkEquivalent = StringVar() #and here's the StringVar() TkEquivalent.set(string(someText)) #and here I set it equal to the normal variable. When someText changes, this variable will too... HOWEVER: TkEquivalent.set("Nobody Expects " + string(someText)) If I do this, the StringVar() will no longer automatically update! How can I include that static text and still have the StringVar() update to reflect changes made to someText? Thanks for your help.

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• Should I use a class in this: Reading a XML file using lxml.

  - by PulpFiction

  Hi everyone. This question is in continuation to my previous question, in which I asked about passing around an ElementTree. I need to read the XML files only and to solve this, I decided to create a global ElementTree and then parse it wherever required. My question is: Is this an acceptable practice? I heard global variables are bad. If I don't make it global, I was suggested to make a class. But do I really need to create a class? What benefits would I have from that approach. Note that I would be handling only one ElementTree instance per run, the operations are read-only. If I don't use a class, how and where do I declare that ElementTree so that it available globally? (Note that I would be importing this module) Please answer this question in the respect that I am a beginner to development, and at this stage I can't figure out whether to use a class or just go with the functional style programming approach.

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• Convert sets to frozensets as values of a dictionary

  - by Space_C0wb0y

  I have dictionary that is built as part of the initialization of my object. I know that it will not change during the lifetime of the object. The dictionary maps keys to sets. I want to convert all the values from sets to frozensets, to make sure they do not get changed. Currently I do that like this: for key in self.my_dict.iterkeys(): self.my_dict[key] = frozenset(self.my_dict[key]) Is there a simpler way to achieve this? I cannot build frozenset right away, because I do not how much items will be in each set until i have built the complete dictionary.

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• How should I use try...except while defining a function?

  - by SpawnCxy

  Hi all, I find I've been confused by the problem that when I needn't to use try..except.For last few days it was used in almost every function I defined which I think maybe a bad practice.For example: class mongodb(object): def getRecords(self,tname,conditions=''): try: col = eval("self.db.%s" %tname) recs = col.find(condition) return recs except Exception,e: #here make some error log with e.message What I thought is ,exceptions may be raised everywhere and I have to use try to get them. And my question is,is it a good practice to use it everywhere when defining functions?If not are there any principles for it?Help would be appreciated! Regards

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• How to optimize this script

  - by marks34

  I have written the following script. It opens a file, reads each line from it splitting by new line character and deleting first character in line. If line exists it's being added to array. Next each element of array is splitted by whitespace, sorted alphabetically and joined again. Every line is printed because script is fired from console and writes everything to file using standard output. I'd like to optimize this code to be more pythonic. Any ideas ? import sys def main(): filename = sys.argv[1] file = open(filename) arr = [] for line in file: line = line[1:].replace("\n", "") if line: arr.append(line) for line in arr: lines = line.split(" ") lines.sort(key=str.lower) line = ''.join(lines) print line if __name__ == '__main__': main()

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• Reverse Search Best Practices?

  - by edub

  I'm making an app that has a need for reverse searches. By this, I mean that users of the app will enter search parameters and save them; then, when any new objects get entered onto the system, if they match the existing search parameters that a user has saved, a notification will be sent, etc. I am having a hard time finding solutions for this type of problem. I am using Django and thinking of building the searches and pickling them using Q objects as outlined here: http://www.djangozen.com/blog/the-power-of-q The way I see it, when a new object is entered into the database, I will have to load every single saved query from the db and somehow run it against this one new object to see if it would match that search query... This doesn't seem ideal - has anyone tackled such a problem before?

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• What framework is trac based on?

  - by user198729

  I just downloaded this tracking system and curious what framework this great system uses?

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• How do I most efficienty check the unique elements in a list?

  - by alex

  let's say I have a list li = [{'q':'apple','code':'2B'}, {'q':'orange','code':'2A'}, {'q':'plum','code':'2A'}] What is the most efficient way to return the count of unique "codes" in this list? In this case, the unique codes is 2, because only 2B and 2A are unique. I could put everything in a list and compare, but is this really efficient?

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• What do I do with a Concrete Syntax Tree?

  - by Cap

  I'm using pyPEG to create a parse tree for a simple grammar. The tree is represented using lists and tuples. Here's an example: [('command', [('directives', [('directive', [('name', 'retrieve')]), ('directive', [('name', 'commit')])]), ('filename', [('name', 'f30502')])])] My question is what do I do with it at this point? I know a lot depends on what I am trying to do, but I haven't been able to find much about consuming/using parse trees, only creating them. Does anyone have any pointers to references I might use? Thanks for your help.

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• How can we change a wx.MenuBar background and foreground colour using wxpython?

  - by aF

  Hello, I want to change the wxpython menubar colours. How can I do it? Thanks in advance :)

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• Counter variable for class

  - by George

  I am having problem getting this piece of code to run. The class is Student which has a IdCounter, and it is where the problem seems to be. (at line 8) class Student: def __init__(self): # Each student get their own student ID idCounter = 0 self.gpa = 0 self.record = {} # Each time I create a new student, the idCounter increment idCounter += 1 self.name = 'Student {0}'.format(Student.idCounter) classRoster = [] # List of students for number in range(25): newStudent = Student() classRoster.append(newStudent) print(newStudent.name) I am trying to have this idCounter inside my Student class, so I can have it as part of the student's name (which is really an ID#, for example Student 12345. But I have been getting error. Traceback (most recent call last): File "/Users/yanwchan/Documents/test.py", line 13, in <module> newStudent = Student() File "/Users/yanwchan/Documents/test.py", line 8, in __init__ idCounter += 1 UnboundLocalError: local variable 'idCounter' referenced before assignment I tried to put the idCounter += 1 in before, after, all combination, but I am still getting the referenced before assignment error, can you explain to me what I am doing wrong? Thank you Edit: Provided the full code I have

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• Passing around an ElementTree

  - by PulpFiction

  Hello. In my program, I need to make use of an ElementTree object in various functions in my program. More specifically, I am doing this: tree = etree.parse('somefile.xml') I am passing this tree around in my program. I was wondering whether this is a good approach, or can I do this: Create a global tree (I come from a C++ background and I know global is bad) Create the tree again wherever required. Or is my approach ok?

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• Rewriting Live TCP/IP (Layer 4) Streams

  - by user213060

  I want to rewrite TCP/IP streams. Ettercap's etterfilter command lets you perform simple live replacements of TCP/IP data based on fixed strings or regexes. Example: if (ip.proto == TCP && tcp.dst == 80) { if (search(DATA.data, "gzip")) { replace("gzip", " "); msg("whited out gzip\n"); } } if (ip.proto == TCP && tcp.dst == 80) { if (search(DATA.data, "deflate")) { replace("deflate", " "); msg("whited out deflate\n"); } } http://ettercap.sourceforge.net/forum/viewtopic.php?t=2833 I would like to rewrite streams based on my own filter program instead of just simple string replacements. Anyone have an idea of how to do this? Is there anything other than Ettercap that can do live replacement like this, maybe as a plugin to a VPN software or something? The rewriting should occur at the transport layer (Layer 4) as it does in this example, instead of a lower layer packet-based approach. Thanks!

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• How do you extend the Site model in django?

  - by John Giotta

  What is the best approach to extending the Site model in django? Creating a new model and ForeignKey the Site or there another approach that allows me to subclass the Site model? I prefer subclassing, because relationally I'm more comfortable, but I'm concerned for the impact it will have with the built-in Admin.

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• nested list comprehension using intermediate result

  - by KentH

  I am trying to grok the output of a function which doesn't have the courtesy of setting a result code. I can tell it failed by the "error:" string which is mixed into the stderr stream, often in the middle of a different conversion status message. I have the following list comprehension which works, but scans for the "error:" string twice. Since it is only rescanning the actual error lines, it works fine, but it annoys me I can't figure out how to use a single scan. Here's the working code: errors = [e[e.find('error:'):] for e in err.splitlines() if 'error:' in e] The obvious (and wrong) way to simplify is to save the "find" result errors = [e[i:] for i in e.find('error:') if i != -1 for e in err.splitlines()] However, I get "UnboundLocalError: local variable 'e' referenced before assignment". Blindly reversing the 'for's in the comprehension also fails. How is this done? THanks. Kent

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• Using SQLAlchemy, how can I return a count with multiple columns

  - by Andy

  I am attempting to run a query like this: SELECT comment_type_id, name, count(comment_type_id) FROM comments, commenttypes WHERE comment_type_id=commenttypes.id GROUP BY comment_type_id Without the join between comments and commenttypes for the name column, I can do this using: session.query(Comment.comment_type_id,func.count(Comment.comment_type_id)).group_by(Comment.comment_type_id).all() However, if I try to do something like this, I get incorrect results: session.query(Comment.comment_type_id, Comment.comment_type, func.count(Comment.comment_type_id)).group_by(Comment.comment_type_id).all() I have two problems with the results: (1, False, 82920) (2, False, 588) (3, False, 4278) (4, False, 104370) Problems: The False is not correct The counts are wrong My expected results are: (1, 'Comment Type 1', 13820) (2, 'Comment Type 2', 98) (3, 'Comment Type 2', 713) (4, 'Comment Type 2', 17395) How can I adjust my command to pull the correct name value and the correct count?

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• sqlalchemy natural sorting

  - by teggy

  Currently, i am querying with this code: meta.Session.query(Label).order_by(Label.name).all() and it returns me objects sorted by Label.name in this manner ['1','7','1a','5c']. Is there a way i can have the objects returned in the order with their Label.name sorted like this ['1','1a','5c','7'] Thanks!

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