[Tutor] Editing files through Python

[Isr Gish]

Hi Bryan,

-----Original Message-----
   >From: "Bryan"<juicebypi216 at yahoo.com>
   >Sent: 9/1/04 2:05:44 PM
   >To: "Bob Gailer"<bgailer at alum.rpi.edu>, "tutor at python.org"<tutor at python.org>
   >Subject: Re: [Tutor] Editing files through Python
   >
   >Hi Bob,
   > 
[snip some text]

   >Here is the program:
   > 
   >input_file = file('C:\BryFolder\coherence.dat', 'r') 
   >lines = input_file.readlines() 
   >output_file = file('C:\BryFolder\coherence.dat', 'w') 
   >for line in lines:
   >   nums = line.split(" ") 
   >   retain = nums[:5] 
   >   new_line = ", ".join(retain)+"\n" 
   >   output_file.write(new_line)   
   >output_file.close()
   > 
   >Here is the error:
   > 
   >Traceback (most recent call last):
   >  File "C:\BryFolder\cohprog3.py", line 1, in ?
   >    input_file = file('C:\BryFolder\kt.1.24.data.036rd.test.dat', 'r') # substitute your path to the file
   >IOError: [Errno 2] No such file or directory: 'C:\\BryFolder\\kt.1.24.data.036rd.test.dat'
   > 

It seems that the file you give in the program is not the same file thatbis showing in the error. 
What the acttual error is saying, is that there is no such file. (which is brobebly related with that that you have a different file in the error)

All the best,
Isr


   >Thanks for the help
   >Bryan
   > 
   > 
   > 
   >
   >
   >Bob Gailer <bgailer at alum.rpi.edu> wrote:At 01:38 PM 8/30/2004, Bryan wrote:
   >>
   >>I am a beginner in Python, and this is my first time using this list so I 
   >>hope my question is acceptable.
   >
   >We are here to help, but not just give answers. However your request seems 
   >to me to merit a program, which I hope you will study to enhance your 
   >understanding of Python. Please ask more questions.,
   >
   >>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?
   >
   >The usual approach is to read the file into a Python variable, process the 
   >variable and write a new file (which can have the same name as the input 
   >file, rather than to attempt to manipulate the file itself. It is a LOT 
   >easier this way.
   >
   >> 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 have written a complete program, just to avoid any ambiguities.
   >
   >input_file = file('num.txt', 'r') # substitute your path to the file
   >lines = input_file.readlines() # list of lines
   >output_file = file('num.txt', 'w') # substitute your path to the file
   >for line in lines:
   >nums = line.split(", ") # assumes numbers separated by ", ", gives list 
   >of numbers
   >retain = nums[:5] # keep first 5 numbers
   >new_line = ", ".join(retain)+"\n" # reassemble into a line
   >output_file.write(new_line) # write to file
   >output_file.close()
   >
   >Please note this depends on consistent number separators. If the separators 
   >vary, then the approach gets more complex.
   >
   >Bob Gailer
   >bgailer at alum.rpi.edu
   >303 442 2625 home
   >720 938 2625 cell 
   >
   >
   >
   >		
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