python - Reading file with comments syntax

Question

Is there an existing way to read any files with python already ignoring characters that are to the right of a comment character (for example, #)?

For example, consider the file

 # this is a comment
 0, 6, 7 # this is a comment
 5, 6, 7 # this is a comment
 7, 6 # this is a comment

I'm looking for something that could already be called as

file.readcomlines()
#or
readcomlines(file)

and return

['0, 6, 7 ', '5, 6, 7 ', '7, 6 ']

Is there such a thing in python or I'm going to have to program this function manually? Web search was of no help at all.

score 0 · Answer 1 · answered May 12 '15 at 12:46

0

You can use the Built-in function str.partition(sep)

line = "0, 6, 7 # this is a comment"
left_part = line.partition("#")[0]

answered May 12 '15 at 12:46

Quoting Eddie

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So your answer is no, there isn't this by default. I have to program it myself using this. Am I right? – TomCho May 12 '15 at 12:49
Won't this solution split on hashes that are part of strings, not comments? – alexwlchan May 12 '15 at 12:49
@alexwlchan: Yes, it would. But it seems that in this scenario there are only integer-list-type parts on the left-hand side of the hash. – Quoting Eddie May 12 '15 at 12:57

score 0 · Answer 2 · answered May 12 '15 at 12:49

You could write a function that does this

def readcomlines(path):
    with open(path) as f:
        return [line.split('#', 1)[0] for line in f if '#' in line]

For example

>>> readcomlines('test.txt')
['', '0, 6, 7 ', '5, 6, 7 ', '7, 6 ']

This is, however, only a crude way to solve this and isn't particularly robust. The character # may show up in a number of other places other than just comments.

python - Reading file with comments syntax

2 Answers2