Python regex inconsistent output between groups() and group()

Question

I am doing a little test to grab backslash (\) using Python regex and what I found is a bit strange.

import re
stringing = "\\"
pattern = re.compile(r'(\\)')
search = pattern.search(string)
print search.group()

The output is shown below, which is as expected

However, when I use .groups() as,

print search.groups()

I get

('\\',)

Which is clearly wrong. Not sure what is happening.

enter image description here

try search.group() alone without print. It will give you '\\' not a backslash. — Avinash Raj
– Avinash Raj, Commented Mar 5, 2015 at 3:33
Yes it does. Why is that though? Isn't it supposed to give only one `\` — hypersonics
– hypersonics, Commented Mar 5, 2015 at 3:36
@AvinashRaj I am running in a Python interpreter opened inside a linux terminal. — hypersonics
– hypersonics, Commented Mar 5, 2015 at 3:41

thefourtheye · Accepted Answer · 2015-03-05 03:42:03Z

4

tl;dr \ is the str representation of the backslash character and '\\' is the repr representation of the backslash character.

In this case, search.group returns a string. The actual string representation of \ is \ only. But, when you print a tuple, it internally calls the repr on all the objects in it. The result of repr on \ is '\\'.

You can check that like this

print repr(search.group()), str(search.group())
# '\\' \

answered Mar 5, 2015 at 3:42

thefourtheye

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