🌐 Mailman 3 May 2002 - Tutor - python.org

Backslashes inside of variable
by Phoebus Nov. 23, 2003

Nov. 23, 2003

I am running Python 2.2 on Win2k. I have a program which writes a filename, with backslashes to a file, along with other stuff. I read the file in using readlines() and put each line into a variable. My problem is I want to use the filename, but I can't use it because of the backslashes. I know about doing open(r"d:\test\file.txt","w") or even open(`d:\test\file.txt`,"w"), but the filename is inside of a variable so when I do open(filename,'w'), I have problems. Can anyone help? Thanks, Steve --

4 6

Why NOT to Use Python?
by Dan Shafer June 2, 2002

June 2, 2002

I'm working on a Python article for CNET. They want me to provide pros and cons for choosing Python in creating a Web-based enterprise-type application where enterprise is defined as meaning lots of simultaneous users. Pros I got. Cons I don't got. Any thoughts either way? Comparing to Java and C# and .NET strategies is probably the order of the day, although I'm open to ideas that don't fit that box.

9 11

RE: [Tutor] Catching the exit
by alan.gauld＠bt.com May 31, 2002

May 31, 2002

> def catchexit(event): > query = askyesno(title='Warning', message='Did you save > your work') > print query > if query == 'Yes': > sys.exit() > else: > return I think this return will now take you into the default handler which will exit anyway. You need to use return "break" to turn off the default behaviour. Alan G

1 0

thread-safe singleton ?
by Praveen Kumar May 31, 2002

May 31, 2002

Are either/both of the below singleton implementations thread-safe ? I'm thinking not, b/c I think there are cases where multiple threads can execute the statement that sets the singleton instance, eg: Singleton.__instance = Singleton.__impl() Singleton.__single = self I'm new to python, so perhaps I'm missing something. Thanks, pk ----- http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52558 class Singleton: """ A python singleton """ class __impl: """ Implementation of the singleton interface """ def spam(self): """ Test method, return singleton id """ return id(self) # storage for the instance reference __instance = None def __init__(self): """ Create singleton instance """ # Check whether we already have an instance if Singleton.__instance is None: # Create and remember instance Singleton.__instance = Singleton.__impl() # Store instance reference as the only member in the handle self.__dict__['_Singleton__instance'] = Singleton.__instance def __getattr__(self, attr): """ Delegate access to implementation """ return getattr(self.__instance, attr) def __setattr__(self, attr, value): """ Delegate access to implementation """ return setattr(self.__instance, attr, value) # Test it s1 = Singleton() print id(s1), s1.spam() s2 = Singleton() print id(s2), s2.spam() # Sample output, the second (inner) id is constant: # 8172684 8176268 # 8168588 8176268 ----------------------------- http://www.python.org/workshops/1997-10/proceedings/savikko.html class Singleton: __single = None def __init__( self ): if Singleton.__single: raise Singleton.__single Singleton.__single = self def Handle( x = Singleton ): try: single = x() except Singleton, s: single = s return single __________________________________________________ Do You Yahoo!? Yahoo! - Official partner of 2002 FIFA World Cup http://fifaworldcup.yahoo.com

2 2

RE: [Tutor] Why NOT to Use Python?
by alan.gauld＠bt.com May 31, 2002

May 31, 2002

> In fact, Java seems to have a rather healthy set of enterprise tools > that a team of team of developers can use in consistent and > predictable ways. This is a good argument. Also the fact that commercial support exists for Java, C# and .NET from companies the bean counters have heard of is a big factor for enterprise size companies. > Java can also present certain performance/speed advantages under many > realistic circumstances. I've seen this claimed lots of times, I've yet to find an example in any of the trials I've done. > Jython also presents the option of creating > 100% pure Java .class files, which addresses performance Errr, no it doesn't. Jython will always be slower than CPython or pure Java simply because it works by using the Java interpreter within the JVM, You get two layers of interpretation. Translating Python bytecodes into java bytecodes gets you portability (to any JVM box) but it doesn't get you performance. > These aren't the only good reasons to do so, of course. Jython, after > all, makes available the libraries of both Java AND Python! This is > nothing to be sniffed at. Integration with Java is a good argument for Jython where a body of Java investment already exists. Green field sites may not get much benefit. Alan g. Author of the 'Learning to Program' web site http://www.freenetpages.co.uk/hp/alan.gauld

1 0

AttributeError in class Today
by Thomas Rivas May 31, 2002

May 31, 2002

Hi all -- Newbie question here: When I rum Listing 10.7 from 'Teach Yourself Python in 24 Hours:' #!/usr/local/bin/python import time import now class today(now.now): def __init__(self, y = 1970): now.now.__init__(self) def update(self,tt): if len(tt) < 9: raise TypeError if tt[0] < 1970 or tt[0] > 2038: raise OverflowError self.t = time.mktime(tt) self(self.t) if __name__ == "__main__": n = today() print "The year is", n.year print n x = today() s = `x` print s tt = (1999, 7, 16, 12, 59, 59, 0, 0, -1) x.update(tt) print x I get the following result with an AttributeError: The year is 2002 <__main__.today instance at 0x83f891c> <__main__.today instance at 0x83f891c> Traceback (most recent call last): File".../py_snips/today, line 22 in ? x.update(tt) File".../py_snips/today, line 13, in update self(self.t) AttributeError: today instance has no __call__ method My question is: What arguments should this __call__ method have?; where should I put it the update() function? Is the problem with the 'now' module that was created and imported? In short, what's happening here? Thank for the help.

2 1

Using time.localtime() and files
by Chris Avery May 31, 2002

May 31, 2002

Hi! I'm writin a script that writes the date, user, and change that that person did to a file called CHANGELOG. This is for a school machine with many student admins. I need the file to look like this: YYYY-MM-DD user * change I know that I need to use time.localtime() and pickle, but I can't get the date to write to the file correctly. Help! Thanks -- +++++++++++++++++++ Chris Avery, KC0KTH +++++++++++++++++++

3 2

Catching the exit
by shendric＠arches.uga.edu May 31, 2002

May 31, 2002

Hi all, I was attempting to write a script that creates a Tkinter window and when you try to close it, it prompts you for confirmation. This is the "Do you want to save your work?" type of interaction found in a lot of software. I tried binding the Destroy event from the root to a function that puts up the window, but the root is destroyed before the window can be put up there. Any ideas? Here's the code: from Tkinter import * from tkMessageBox import askyesno import sys def catchexit(event): query = askyesno(title='Warning', message='Did you save your work') print query if query == 'Yes': sys.exit() else: return root = Tk() root.bind('<Destroy>', catchexit) root.mainloop()

1 0

A very simple question
by Nicole Seitz May 31, 2002

May 31, 2002

Hi there! I'd like to write a function that gets a list , checks if there are only strings in the list starting with a lowercase letter and then returns 1 if only lowercase, 0 if not. How can I do that? example list: myList = [ "abc", "def", "Cde"] If I write: def checkIfOnlyLower(list): for item in list: if item[0].islower(): return 1 else: return 0 the function will return 1 as soon as it comes to the first string starting with a lowercase letter.But that's not what I want. Hope you can help me. Thanks in advance. Nicole

6 5

reading a list of files from a directory (WinXP)
by Matthew Huggett May 31, 2002

May 31, 2002

Hi: I would like to read a list of files (all with the extension .tfm) from a directory, strip off their .tfm extensions, and put them into a list (i.e., myList = [file1,file2,etc...]). What would be the most efficient way of doing this? Do I first need to list the files in a source file-- "C:\ dir /b > MyFiles.txt"-- or can I read from the directory directly?

2 1