RegEx Help

[mp3909]

import re
dummy = re.compile('XXX\WYYY')
mo = dummy.search('the letters XXX\YYY')
mo.group()

Can someone please explain why

mo.group()

kicks back

'XXX\\YYY'

- I thought it should kick back

'XXX\YYY'

i.e. just 1 backslash in between the letters not 2.

[snippsat]

>>> import re
>>> dummy = re.compile('XXX\WYYY')
>>> mo = dummy.search('the letters XXX\YYY')

>>> mo.group()
'XXX\\YYY'
>>> # It magically goes away with print()
>>> print(mo.group())
XXX\YYY
>>> # No really
>>> print(repr(mo.group()))
'XXX\\YYY'
>>>

It's this way because of escape characters.
Example \n it's a newline character.
We see only one \,because it's a escape character.

>>> s = '\n'
>>> s
'\n'
>>> print(s)


>>> 

\Y is not a escape character.

>>> s = '\Y'
>>> s
'\\Y'
>>> print(s)
\Y
>>> 

Also a tip for regex should always use raw string in expression,then will not get a surprise with escape character.
Then it look like this:
dummy = re.compile(r'XXX\WYYY')