[Tutor] Editing files through Python

[Kent Johnson]

Bryan,

Can you show us what you have so far for reading the files? Do you know how 
to write them?

You probably want to process the files line-by-line. There are several ways 
to process strings. If your data is very regular, string.split() might be 
helpful to divide the line up:
 >>> "1, 2, 3, 4, 5, 6, 7, 8, 9, 10".split(", ")
['1', '2', '3', '4', '5', '6', '7', '8', '9', '10\n']

Notice the newline is part of the last split. You can use list slicing to 
drop the end of the list:
 >>> ['1', '2', '3', '4', '5', '6', '7', '8', '9', '10'][:-5]
['1', '2', '3', '4', '5']

Finally use join to put the list back together for output:
 >>> ", ".join(['1', '2', '3', '4', '5'])
'1, 2, 3, 4, 5'

If your data is not as regular as this, you have to think of another way 
for the program to identify the place to cut the string.

Kent

At 12:38 PM 8/30/2004 -0700, Bryan wrote:
>Hi,
>
>I am a beginner in Python, and this is my first time using this list so I 
>hope my question is acceptable.
>
>Basically, my goal is to read data files that are already on my hard drive 
>into Python, and then edit them, deleting unneccesary portions of data.
>
>I have already figured out how to read the files into Python, I just 
>cannot figure out how to edit them.  Here are the difficulties:
>
>How do I delete, cut, or paste portions of the data I am reading and how 
>do I tell the program to jump to that specific portion of data that I want 
>to alter?
>
>Here is a somewhat complicated example, similar to what I want to do -
>
>I have two rows of numbers, as shown below.  Each row has 10 numbers 
>(hopefully they will show up as two rows of numbers in the email (1-10 and 
>11-20).
>
>1, 2, 3, 4, 5, 6, 7, 8, 9, 10
>11, 12, 13, 14, 15, 16, 17, 18, 19, 20
>
>What commands might I use to automatically go through each row, deleting 
>the 6th through 10th numbers in each row (6-10 in the first row and 16-20 
>in the second row).
>
>I would like to write a program because I have hundreds of rows like this.
>
>I appreciate any help
>
>Thanks
>Bryan
>
>
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