How to handle AttributeError in python?

Question

I am working through some example code which I've found on What's the most efficient way to find one of several substrings in Python?. I've changed the code to:

import re
to_find = re.compile("hello|there")
search_str = "blah fish cat dog haha"
match_obj = to_find.search(search_str)
#the_index = match_obj.start()  
which_word_matched = ""
which_word_matched = match_obj.group()

Since there is now no match , I get:

Traceback (most recent call last):
File "<console>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'group'

What is the standard way in python to handle the scenario of no match, so as to avoid the error

score 4 · Answer 1 · answered Jan 13 '14 at 18:05

4

match_obj = to_find.search(search_str)
if match_obj:
    #do things with match_obj

Other handling will go in an else block if you need to do something even when there's no match.

answered Jan 13 '14 at 18:05

roippi

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score 3 · Accepted Answer · answered Jan 13 '14 at 18:05

3

Your match_obj is None because the regular expression did not match. Test for it explicitly:

which_word_matched = match_obj.group() if match_obj else ''

answered Jan 13 '14 at 18:05

Martijn Pieters

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Much appreciated - Bill – user1592380 Jan 13 '14 at 18:09
This is an interesting way to phrase it. I haven't seen this before. – user1592380 Jan 13 '14 at 18:52

How to handle AttributeError in python?

2 Answers2