Re: [Tutor] Variables don't change when altered within a loop?
> Hi, I just started picking up python
yesterday, and have already come> across something that has me
stumped. I want some code that does> this:> > a =
foo(a)> b = foo(b)> c = foo(c)> > So I try to do
this with a for loop, like so:> > for i in [a, b,
c]:> i = foo(i)> print
i # make sure that it worked correctly> >
So far, so good. The problem is that outside the loop, the values>
aren't changed. For example,
You need to understand the difference
between names
and variables and values. A variable in
Python is a reference
to a value (or more correctly an object
which has a value)
for i in [a,b,c]
makes a new variable(name) i which takes on
the *values*
of a,b,c in turn with each iteration of the
loop.
i does not take on the name a,b or c, it
takes on the value.
Thus in the first iteration the variable i
will take on the
value referenced by a, in the second
iteration the value
referenced by b and in the third iteration
the value
referenced by c. The original variables
still refer
to their original values.
i = foo(a)
now i will be rebound to the value returned
by the function
foo() when passed the value of a as an
argument. The value
refered to by a has not been changed in any
way.
print i
prints the new value associated with i. It
changes nothing.
in the second iteration the same happens
but with i
taking on the initial value of
b.
Lets look at a more concrete
example:
def foo(x): return x + 10
a,b,c = 1,2,3
code
iter 1 iter
2 iter 3
for i in
[a,b,c]: i =
1 i =
2 i = 3
i =
foo(i) i
= 11 i =
12i = 13
Note that a,b,c are not changed anywhere in
this loop.
They retain the original values of
1,2,3.
If you wanted to change them you would need
to explicitly
set their values
> What is going on?
> Why aren't the values of my variables
changing when> I change them inside a loop like this?
You are not changing the variables you are
changing i
which is an entirely different
variable!
The normal way to do what I think you want
is to
put the variables in a list or dictionary,
then
you can loop over that and change the
values.
Like so:
vars = {'a':1, 'b':2,'c':3}
def foo(x): return x+10
for key,value in vars.items():
vars[key] =
foo(value)
print vars
HTH,
Alan GauldAuthor of the Learn to
Program web sitehttp://www.freenetpages.co.uk/hp/alan.gauld
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Re: [Tutor] Wiget
> The problem is at the end where i try and get the number of > Tries the user has tried it would just reset everytime the button > in clicked, so my question is how would i go about getting > the number of times the button is clicked and the anwser is wrong. >def number_anwser(self): >guess = self.guess_ent.get() >guess = int(guess) >response = "" >tries = 1 You are resetting tries to one every time. You need to store tries atthe object level by creating a self.tries in your init method. You can then increment self.tries in the code below. > >if (guess < the_number): >response += "Higher" >tries += 1 >elif (guess > the_number): >response += "Lower" >tries += 1 >else: >tries = str(tries) and this would become tries = str(self.tries) that is, you don't want to convert self.tries to a string! >response += "Correct! that was my number, \n" >response += "You guessed it in just " >response += tries >response += " tries!" > >self.response_txt.delete(0.0, END) >self.response_txt.insert(0.0, response) > HTH Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Python urllib (linux)
Hi all, I'm doing some failure testing for a python script that uses urllib and urllib2 to open a web page and post data. If the server's apache is down or if I change the ip address the script is trying to contact to be a bogus address, the script handles it prefectly. When I unplug the ethernet cable from my machine (client), the script hangs. Is there a way I can implement a timeout to handle this problem? I'd appreciate any suggestions because I'm clueless. Thanks, Patty ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Python urllib (linux)
On Fri, 2006-06-30 at 13:58 +, Patty wrote: > Hi all, > I'm doing some failure testing for a python script that uses urllib and > urllib2 > to open a web page and post data. If the server's apache is down or if I > change > the ip address the script is trying to contact to be a bogus address, the > script > handles it prefectly. When I unplug the ethernet cable from my machine > (client), > the script hangs. Is there a way I can implement a timeout to handle this > problem? import socket if not socket.getdefaulttimeout(): socket.setdefaulttimeout(25.0) This sets a timout of 25 seconds. You need to set the timeout BEFORE using a socket. The documentation is in the socket module, should you need more detail. This technique works for simple cases. > I'd appreciate any suggestions because I'm clueless. > Thanks, > Patty > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor -- Lloyd Kvam Venix Corp ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Python urllib (linux)
On Fri, 30 Jun 2006, Patty wrote:
> I'm doing some failure testing for a python script that uses urllib and
> urllib2 to open a web page and post data Is there a way I can
> implement a timeout to handle this problem?
I don't have any firsth-hand knowledge on this, but
http://www.voidspace.org.uk/python/articles/urllib2.shtml says:
By default the socket module has no timeout and can hang. Currently, the
socket timeout is not exposed at the httplib or urllib2 levels. However,
you can set the default timeout globally for all sockets using :
import socket
import urllib2
# timeout in seconds
timeout = 10
socket.setdefaulttimeout(timeout)
# this call to urllib2.urlopen now uses the default timeout
# we have set in the socket module
req = urllib2.Request('http://www.voidspace.org.uk')
response = urllib2.urlopen(req)
Good luck!
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Re: [Tutor] Python urllib (linux)
Hi again, > > problem? > import socket > if not socket.getdefaulttimeout(): > socket.setdefaulttimeout(25.0) > I'm sorry I forgot to mention that I'm using python 2.2.3, and this version doesn't have those methods. Patty ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Unit testing
Terry Carroll schrieb: > You can just use a series of Queues, where each Queue represents the work > being passed from one thread to the other. If you want, you can have a look at my threadpool module, which implements exactly this pattern. It is basically nothing more than an elaborate example on this technique: http://chrisarndt.de/en/software/python/threadpool/ Chris begin:vcard fn:Christopher Arndt n:Arndt;Christopher adr:Fort Lorenzo;;Cuan Na Coille;Galway;Co. Galway;;Irland email;internet:[EMAIL PROTECTED] tel;work:+353 (0)91-745500 tel;cell:+353 (0)86-3378101 x-mozilla-html:TRUE url:http://chrisarndt.de version:2.1 end:vcard ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] saving output in a text file
Hi, my name is Hafsa
I am new to programming in Python. Basically i am working with regular _expression_ matching using Python. I have a problem with saving output from the regular _expression_ matches in a text file. Can you guide me how to save the output returned by a regular _expression_ group, into a text file? for instance for the following regular _expression_:
r1= re.compile("""(?PTYPE=\"PER\"\sSUBTYPE=\"Individual\")(?P.*?\<)
""",re.VERBOSE)
If the above regular _expression_ is searched for in a file, how can i save the output matches from the group "name" into a new text file?
Thanks & regards,
HafsaFREE pop-up blocking with the new MSN Toolbar MSN Toolbar Get it now!
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Re: [Tutor] classes and functions
> -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of anil maran > Sent: Thursday, June 29, 2006 12:51 PM > To: Tutor > Subject: [Tutor] classes and functions > > how to use classes and functions in python > thanks What do you need to know? Have you read the tutorial? http://pytut.infogami.com/ The tutorial wiki has some info about functions http://pytut.infogami.com/node6.html There's also some information on classes http://pytut.infogami.com/node11-baseline.html Post specific questions if these links aren't clear enough, and we can probably help. I hope these links help you. Mike http://users.adelphia.net/~mahansen/programming/ ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] saving output in a text file
Hi Hafsa, > Can you guide me how to save the output returned by a regular expression > group, into a text file? for instance for the following regular > expression: [regex cut] > If the above regular expression is searched for in a file, how can i > save the output matches from the group "name" into a new text file? I'm not sure the problem you have has to do with regular expressions. Do you mind if we change the question to something slightly different? If you were given a function that takes a string and returns another string, could you write a program that uses it and writes the result to disk? For example, let's say that we have a string like "hello world", process it through, well: def double(s): "double: string -> string doubles up the input string s." return s + s Would you be able to write a program that takes "hello world", runs it through double(), and writes out "hello worldhelloworld" to disk? What I'm trying to isolate the problem: does it have to do with input/output, or regular expressions, or something else? Best of wishes! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] saving output in a text file
>def double(s):
>"double: string -> string
>doubles up the input string s."
>return s + s
Gaah. Typos. My apologies. Here's a correction to double()
def double(s):
"""double: string -> string
Doubles up the input string s. For example, double("abc")
should return "abcabc".
"""
return s + s
> Would you be able to write a program that takes "hello world", runs it
> through double(), and writes out "hello worldhelloworld" to disk?
I meant to say that the expected content of the file should be:
"hello worldhello world"
My apologies; I rushed that message too quickly.
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