Question

Can someone explain this weird behavior of python re? Obviously the string ‘test’ does not contain either ‘Bid’ or ‘Ask’. Why is this matching?

import re
pat=r'[Bid|Ask]'
reg=re.compile(pat)
if reg.search('test'): print "matched!"

…
matched!

Answer 1

[...]defines a character class, matching any character listed inside. What you wanted is par = r'(Bid|Ask)'.

However, you should not use regex for this at all, do the following instead:

if whatever in ('Bid', 'Ask'):
    # it's one of these two
else:
    # it isn't

If you need to perform a substring check (thanks @agf):

if any(word in whatever for word in ('Bid', 'Ask')):
    # one of the words is in the sting whatever