Regex 'sre_constants.error: bad character range' in large regex pattern

Question

The following is the error message:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/re.py", line 194, in compile
    return _compile(pattern, flags)
  File "/usr/lib/python2.7/re.py", line 251, in _compile
    raise error, v # invalid expression
sre_constants.error: bad character range

This is my object:

>>> re101121=re.compile("""(?i)激[ _]{0,}活[ _]{0,}邮[ _]{0,}箱|(click|clicking)[ _]{1,}[here ]{0,1}to[ _]{1,}verify|stop[ _]{1,}mail[ _]{1,}.{1,16}[ _]{1,}here|(click|clicking|view|update)([ _-]{1,}|\\xc2\\xa0)(on|here|Validate)[^a-z0-9]{1}|(點|点)[ _]{0,}(擊|击)[ _]{0,}(這|这|以)[ _]{0,}(裡|里|下)|DHL[ _]{1,}international|DHL[ _]{1,}Customer[ _]{1,}Service|Online[ _]{1,}Banking|更[ _]{0,}新[ _]{0,}您[ _]{0,}的[ _]{0,}(帐|账)[ _]{0,}户|CONFIRM[ _]{1,}ACCOUNT[ _]{1,}NOW|avoid[ _]{1,}Account[ _]{1,}malfunction|confirm[ _]{1,}this[ _]{1,}request|verify your account IP|Continue to Account security|继[\\s-_]*续[\\s-_]*使[\\s-_]*用|崩[\\s-_]*溃[\\s-_]*信[\\s-_]*息|shipment[\\s]+confirmation|will be shutdown in [0-9]{0,} (hours|days)|DHL Account|保[ ]{0,}留[ ]{0,}密[ ]{0,}码|(Password|password|PASSWORD).*(expired|expiring)|login.*email.*password.*confirm|[0-9]{0,} messages were quarantined|由于.*错误(的)?(送货)?信息|confirm.*(same)? password|keep.*account secure|settings below|loss.*(email|messages)|simply login|quick verification now""")

Answer 1

After minimization, your error boils down to re.compile("""[\\s-_]"""). This is a bad character range indeed; you probably meant the dash to be literal re.compile(r"[\s\-_]") (always use raw strings for regex r"..."). Moving the dash to the end of the bracket group works too: r"[\s_-]".

In the future, try to binary search to find the minimal failing input: remove the right half of the regex. If it still fails, the problem must have been in the left half. Remove the right half of the remaining substring and repeat until you're down to a minimal failing case. This technique doesn't always work when the problem spans both halves, but it can't hurt to try.

As mentioned in the comments, it's pretty odd to have such a massive regex as this, but I'll assume you know what you're doing.

As another aside, there are some antipatterns in this regex (pardon the pun) like {0,} which can be simplified to *.