How to remove '#' comments from a string?

Question

The problem: Implement a Python function called stripComments(code) where code is a parameter that takes a string containing the Python code. The function stripComments() returns the code with all comments removed.

I have:

def stripComments(code):
   code = str(code)
   for line in code:
       comments = [word[1:] for word in code.split() if word[0] == '#']
       del(comments)
stripComments(code)

I'm not sure how to specifically tell python to search through each line of the string and when it finds a hashtag, to delete the rest of the line. Please help. :(

Solution 1

You could achieve this through re.sub function.

import re
def stripComments(code):
    code = str(code)
    return re.sub(r'(?m)^ *#.*\n?', '', code)

print(stripComments("""#foo bar
bar foo
# buz"""))

(?m) enables the multiline mode. ^ asserts that we are at the start. <space>*# matches the character # at the start with or without preceding spaces. .* matches all the following characters except line breaks. Replacing those matched characters with empty string will give you the string with comment lines deleted.

Solution 2

def remove_comments(filename1, filename2):
    """ Remove all comments beginning with # from filename1 and writes
    the result to filename2
    """

    with open(filename1, 'r') as f:
        lines = f.readlines()

    with open(filename2, 'w') as f:
        for line in lines:
            # Keep the Shebang line
            if line[0:2] == "#!":
                f.writelines(line)
            # Also keep existing empty lines
            elif not line.strip():
                f.writelines(line)
            # But remove comments from other lines
            else:
                line = line.split('#')
                stripped_string = line[0].rstrip()
                # Write the line only if the comment was after the code.
                # Discard lines that only contain comments.
                if stripped_string:
                    f.writelines(stripped_string)
                    f.writelines('\n')

Comments

[Avinash Raj]

an example would be better.

[Destiny Brown]

I wasn't given an example... And i'm not sure how it is supposed to look.

[Asclepius]

Consider distutils.text_file.TextFile(file=io.StringIO(code)).readlin‌​es() which uses TextFile with StringIO as needed.

[rerx]

Note that this will not remove comments at the ends of active code lines.

[Bastien]

note if a line of code were to contain '#' as part of the code this would also not work even if you fixed it to work after active code lines by removing the ^ from the regex string

[Bastien]

This would end up badly if # was contained in a string as part of the code