[Tutor] saving output in a text file (fwd)

Danny Yoo dyoo at hkn.eecs.berkeley.edu
Sat Jul 1 19:40:20 CEST 2006


> If we want to create a text file and write some text into it we use the 
> following command in Python:
>
> myfile = open("test.txt","w")<?xml:namespace prefix = o ns =
> "urn:schemas-microsoft-com:office:office" />
>
> myfile.write("hello world")
>
> But what if instead of writing the text 'hello world', i want to write 
> the output returned by a regular expression pattern, into the text file, 
> how would we specify that in the write command.


Just as a disclaimer: I am doing my utmost not to give out The Answer 
here.  So if it sounds like I'm not being very direct, that's precisely 
because you have a good intuition.  *grin* I'm trying to poke at the 
source of the problem, and not the immediate side effects.



You still haven't tackled my initial question about:

>     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 worldhello world" to disk?

Can you try this mini-problem first?  What you've done doesn't touch on 
the question: would you know how to use double() as a part of the write()?

Note that this is just a variation of your original question, replacing 
the regex part with the use of a helper function.  It seems like this 
should be even easier than the problem you're having now.

Here's why I'm asking this: if you're getting stuck at this point too, 
then I'll assume that the problem is that you are unfamiliar with using 
helper functions and function composition.  Then the group as a whole can 
help you with that, since that's a fundamental programming skill that 
you'll want to develop.

But if you can do the mini-exercise, then the focus shifts to the use of 
regular expressions, and things become much easier, since it'll mean that 
you're not familiar with the regex API.


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