How do I read the first line of a string?

Use str.partition() to split the string on a newline, and grab the first item from the result:

my_string.partition('\n')[0]

This is the most efficient method if you only need to split a string in a single location. You could use str.split() too:

my_string.split('\n', 1)[0]

You do then need to tell the method to only split once, on the first newline, as we discard the rest.

Or you could use the .splitlines() method:

my_string.splitlines()[0]

but this has to create separate strings for every newline in the input string so is not nearly as efficient.

readline is used i conjuction with a stream. you could use StringIO if you insist on using readline:

from StringIO import StringIO

sio = StringIO(my_string)
for sline in sio.readlines():
    print sline

I would do

 for line in my_string.split('\n'):
        print line

or do

import re
for line in re.split('\n', my_string):
    print line

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