Question

I have a code that search if a line begin with a specified word and if it does, it changes that whole line with a specified input. However, it doesn’t work for some lines if the line is indented by spaces? Is there a way to read the text directly and ignore the spaces.

Here is the code: (with comments on where the problem is)

import os

def template(filein):
    currdir = os.getcwd() # get current directory
    new_file = open(os.path.join(currdir,'maindir','template.in'),'wt')
    old_file = open(filein)
    for line in old_file:
        if line.startswith('   indent'):
            # this part works well because I put the exact number of spaces present in the text before the search word
            new_file.write('   indent == %s \n' % str('%(indent)s'))
        elif line.startswith('noindent'):
            # this part can't find noindent because i didn't specify the spaces before that that is present in the text
            new_file.write('noindent == %s \n' % str('%(noindent)s'))
        else:
            new_file.write(line)
    new_file.close()
    old_file.close()

Thanks

EDIT: I want to preserve all the spaces present in the original file, even in the lines that I modified.

Answer 1

You can use lstrip to remove the whitespace from the beginning (left) of a line:

for line in old_file:
    stripped_line = line.lstrip()
    # do your matching here against `stripped_line` instead of `line`
    # `line` still contains the original, non-stripped line

On a sidenote, I recommend using with open('filename') as new_file, instead of what you’re doing now. This creates a block in which the file is available and makes sure the file is closed at the end of the block. See the end of this section in the docs.