In Python: how do I say: if line.partition('#' or 'tab') ... do something...

Question

In Python: how do I say:

line = line.partition('#' or 'tab')[0]   ... do something with

I know I can do:

line = line.partition('#')[0]  ... do something

But what is the code for the tab character, and can I say # or tab?

Update: I'm trying to say read the first word on each line, if you read a # then ignore everything after that character (as it is a comment). But then I found if I had in the file first word tab #, then it would read the tab as part of the first word. So I was trying to say, if you read a tab or a hash, then treat the line as a comment. A work around is to just put a space after the first word rather than a tab. But it is not very elegant. I realize now that the if statement was incorrect, I was trying to simplify things too much. Above is now correct, but I think Ned Batchelder's way is the way to go now, but perhaps there is something else now that you know what I'm trying to do.

Answer 1

partition doesn't allow for options, so you may need re.split:

re.split("(#|\t)", line, 1)

re.split has the interesting property that if the pattern is enclosed in parens, then the separator is returned in the results, and you can use maxsplit (as I have here set to 1). This will return a three-tuple similar to partition.

But you're testing the return value of partition, which is always True, so I'm not sure what you're trying to acheive...

Answer 2

'\t' is the string containing a tab.

import re

match = re.search('[#\t]', line)
if match:
    i, j = match.span()
    return (line[:i], line[i:j], line[j:])
return (line, '', '')

This will give results similar to partition: a tuple of (head, sep, tail).

Answer 3

Since the comment is from # to end-of-line, what we usually do is this.

raw_data, _, _ = line.partition("#")
data= raw_data.strip()
if len(data) == 0:
    continue # or whatever, the data part of the line is empty
# you have data

The point is to not try and combine the comment processing with the whitespace stripping.

[The raw_data, _, _ = line.partition("#") will save the part before "#" in raw_data, it will save the "#" in a variable named _. It will also save the part after the "#" in the variable named _. We're just going to ignore the variable named _, so we don't care what value it has.]

You can also do this

data, _, _ = line.strip().partition("#")

This isn't a general solution because sometimes that whitespace in front of the comment is meaningful.