regex - Python 3.x AttributeError: 'NoneType' object has no attribute 'groupdict'

Question

Being a beginner in python I might be missing out on some kind of basics. But I was going through one of the codes from a project and happened to face this :

AttributeError: 'NoneType' object has no attribute 'groupdict'

Following is the section of code,re-phrased though,still this does result in the same problem.

import re

fmt = (r"+((?P<day>d+)d)?((?P<hrs>d+)h)?((?P<min>d+)m)?"
       r"((?P<sec>d+)s)?((?P<ms>d+)ms)?$")
p = re.compile(fmt)
match = p.search('Total run time: 9h 34m 9s 901ms realtime, 7h 6m 29s 699ms uptime')
try:
    d = match.groupdict()
except IndexError:
    print("exception here")

Answer 1

Regular expression functions in Python return None when the regular expression does not match the given string. So in your case, match is None, so calling match.groupdict() is trying to call a method on nothing.

You should check for match first, and then you also don’t need to catch any exception when accessing groupdict():

match = p.search('Total run time: 9h 34m 9s 901ms realtime, 7h 6m 29s 699ms uptime')
if match:
    d = match.groupdict()

In your particular case, the expression cannot match because at the very beginning, it is looking for a + sign. And there is not a single plus sign in your string, so the matching is bound to fail. Also, in the expression, there is no separator beween the various time values.

Try this:

>>> expr = re.compile(r"((?P<day>d+)d)?s*((?P<hrs>d+)h)?s*((?P<min>d+)m)?s*((?P<sec>d+)s)?s*(?P<ms>d+)ms")
>>> match = expr.search('Total run time: 9h 34m 9s 901ms realtime, 7h 6m 29s 699ms uptime')
>>> match.groupdict()
{'sec': '9', 'ms': '901', 'hrs': '9', 'day': None, 'min': '34'}