Question

python 2.6.8

s= '''
foo 
bar
baz
'''
>>>re.findall(r'^\S*',s,re.MULTILINE)
['', 'foo', 'bar', 'baz', '']
>>>ptrn = re.compile(r'^\S*',re.MULTILINE)
>>>ptrn.findall(s)
['', 'foo', 'bar', 'baz', '']
>>>ptrn.findall(s,re.MULTILINE)
['baz', '']

Why is there a difference between using MULTILINE flag in findall?

Answer 1

When calling the findall() method on a regex object, the second parameter is not the flags argument (because that has already been used when compiling the regex) but the pos argument, telling the regex engine at which point in the string to start matching.

re.MULTILINE is just an integer (that happens to be 8).

See the docs.