Text file manipulation.

[joe1986]

Hi there, im trying to create a python program that can read a text file line by line and search for specified words/text/strings and remove them from the text file. Then finally save the modified text file to an output file. The only problem is, the text file contains code for a BACKSPACE typed in the text. e.g. "<BACKSPACE>" this needs to be removed which sounds quite simple, but often there are numbers involved. e.g. "<BACKSPACE: 4>" which would represent 4 backspaces, and so the string needs to be removed and 4 backspaces take place on the text before the code. e.g. "repatre<BACKSPACE: 4>resent" would become "represent" I know a search and delete script that can search for a word at the beggining of the line and then delete the whole line, but im not sure about this. Any ideas would be great.
Cheers,
Joe

[v0id]

You need to look into regular expressions to search in the way as you want to. Python has a standard library for this, called re. It's pretty simple to use, so it doesn't take long to learn the basics of the functions. There's a lot of tutorials on the internet which can get you started.

Are you having problems with reading/writing files as well?

[joe1986]

Originally Posted by v0id

You need to look into regular expressions to search in the way as you want to. Python has a standard library for this, called re. It's pretty simple to use, so it doesn't take long to learn the basics of the functions. There's a lot of tutorials on the internet which can get you started.

Are you having problems with reading/writing files as well?

Cheers for the reply.
I have been having a look at the re library and have (with a little help off a guy on another forum) come up with a program, that seems logical but im having problems writing the results to a txt file, or even to the screen. I know the basics off creating variables for the input/output txt files but still no luck.

[v0id]

# Write to screen
print YourVariable

# Write to file
Filename = "yourfilename"
FileHandle = open(Filename, 'w') # Open the file for writing
FileHandle.write(YourVariable) # Write YourVariable to the file
FileHandle.close() # Close the file again

[joe1986]

Originally Posted by v0id

# Write to screen
print YourVariable

# Write to file
Filename = "yourfilename"
FileHandle = open(Filename, 'w') # Open the file for writing
FileHandle.write(YourVariable) # Write YourVariable to the file
FileHandle.close() # Close the file again

Thanks for that info. Really helped.
Joe

[v0id]

If you have other problems, then just ask!

Good luck with your project.

[joe1986]

Originally Posted by v0id

If you have other problems, then just ask!

Good luck with your project.

Hi V0id,

Here is a solution (so far seems to work.) I can write results to a txt file which is great. All I need to do now is read from a text which im guessing will just go in place of the 'test' section in the code and to be able to iterate this code so that I can run through a whole paragraph containing multiple <BACKSPACE> sections removing all (rather than getting to the first one and terminating.) Would you have any ideas looking at this to do such a thing? Any help would be great. Cheers. Joe

#! /usr/bin/python


import re

# Global variable

bs = re.compile('<BACKSPACE(:[ ]*[0-9]+)?>')
#theInFile = open("test2.txt", "r")
theOutFile = open("backspace_out.txt", "w")

tests = ['re <BACKSPACE>present', 'This is bound to repatreaaaabbbbcccc <BACKSPACE: 17>resent']


def bs_remove(s):

    global bs

    for m in bs.finditer(s):

        if m.groups()[0] is None:

            return s[:m.start() - 1] + s[m.end():]

        else:

            return s[:m.start() - int(m.groups()[0][1:])] + s[m.end():]


for s in tests:

      theOutFile.write (bs_remove(s)+ " ")

[v0id]

Sorry, but I can't help you on this one. I'm not as good in Python as I've been. I took a look at it, and everything seems fine, but the result isn't like you say yourself. But I haven't managed to find out what's wrong.

[monkey_instinct]

import re

def remove_backspace(in_filename, out_filename):
  in_file = open(in_filename,'r')  # Open the input file
  out_file = open(out_filename,'w')  # Open the output File
  r = re.compile('<BACKSPACE(:[ ]*[0-9]+)?>')  # The regex

  for line in in_file:  # Iterates over the lines of the input file
    line_without_backspace = r.sub('', line)  # Replace every match of the regex with an empty string
    out_file.write( line_without_backspace )  # Write the resulting line to the file

  in_file.close()  # Close input file
  out_file.close()  # Close output file

I think that will do it.

[v0id]

@monkey_instinct: He's not trying to delete every match of the regular expression. If you read his previous posts, you can see he wants the <BACKSPACE X> to delete X characters.

ABCDEF<BACKSPACE 2>
=>
ABCD