字符之间的python正则表达式匹配

Question

I'm doing a pretty straightforward regex in python and seeing some odd behavior when I use the "or" operator.

I am trying to parse the following:

>> str = "blah [in brackets] stuff"

so that it returns:

>> ['blah', 'in brackets', 'stuff']

To match the text between brackets, I am using look behind and look ahead, ie:

>> '(?<=\[).*?(?=\])'

If used alone this does indeed capture the text in brackets:

>> re.findall( '(?<=\[).*?(?=\])' , str )
>> ['in brackets']

But when I combine the or operator to parse the strings between spaces, the bracket-match somehow breaks down:

>> [x for x in re.findall( '(?<=\[).*?(?=\])|.*?[, ]' , str ) if x!=' ' ] 
>> ['blah', '[in ', 'brackets] ']

For the life of me I can't understand this behavior. Any help would be appreciated.

Thanks!

Answer 1

You can do:

>>> s = "blah [in brackets] stuff"

>>> re.findall(r'\b\w+\s*\w+\b', s)
['blah', 'in brackets', 'stuff']

Answer 2

For those interested, this is the successful regex that I ended up going with. There is probably a more elegant solution somewhere but this works:

>>> s = "blah 2.0 stuff 1 1 0 [in brackets] more stuff [1]"

>>> brackets_re = '(?<=\[).*?(?=\])'
>>> space_re = '[-\.\w]+(?= )'
>>> my_re = brackets_re + '|' + space_re

>>> re.findall(my_re, s)
['blah', '2.0', 'stuff', '1', '1', '0', 'in brackets', 'more', 'stuff', '1']

Answer 3

If you are looking for an easy way to do this, then use this. Note : I replaced str with string as 'str' is a built-in function of python.

import re
string = "blah [in brackets] stuff"
f = re.findall(r'\w+\w', string)
print(f)

Output: ['blah', 'in brackets', 'stuff']

Answer 4

The answers so far don't take into account that you may have more than 2 words inside the brackets, or even one word. The following regex will split on the brackets and any leading or trailing white space of the brackets. It will also work if there are more bracketed content in the string.

s = "blah [in brackets] stuff"

s = re.split(r'\s*\[|\]\s*', s) # note the 'or' operator is used and literal opening and closing brackets '\[' and '\]'

print(s)

output: ['blah', 'in brackets', 'stuff']

And an example using a string with different amounts of words inside brackets and using several sets of brackets:

s = "blah [in brackets] stuff [three words here] more stuff [one-word] stuff [a digit 1!] stuff."

s = re.split(r'\s*\[|\]\s*', s)

print (s)

output: ['blah', 'in brackets', 'stuff', 'three words here', 'more stuff', 'one-word', 'stuff', 'a digit 1!', 'stuff.']