Using Variables instead of pattern in Regular Expression

Question

I am fairly new to python. I have searched several forums and have not quite found the answer.

I have a list defined and would like to search a line for occurrences in the list. Something like

import re
list = ['a', 'b', 'c']

for xa in range(0, len(list)):
m = re.search(r, list[xa], line):
if m:
    print(m)

Is there anyway to pass the variable into regex?

Your question is not clear - what is the variable r ? you should describe what you're trying to do (example input + output). — Nir Alfasi
– Nir Alfasi, Commented May 3, 2015 at 2:05
What are you doing with the re.search? And what do you mean "search a line for occurrences in the list"? Just fyi, proper indentation is required for your for loops, and if you pass in 3 arguments to re.search, the third argument will be interpreted as a keyword argument: flags. — Shashank
– Shashank, Commented May 3, 2015 at 2:17

Avinash Raj · Accepted Answer · 2015-05-03 02:00:48Z

1

yep, you could do like this,

for xa in range(0, len(lst)):
    m = re.search(lst[xa], line)
    if m:
        print(m.group())

Example:

>>> line = 'foo bar'
>>> import re
>>> lst = ['a', 'b', 'c']
>>> for xa in range(0, len(lst)):
        m = re.search(lst[xa], line)
        if m:
            print(m.group())


a
b

answered May 3, 2015 at 2:00

Avinash Raj

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Comments

Stefan Pochmann · Accepted Answer · 2015-05-03 02:34:33Z

0

You can build the variable into the regex parameter, for example:

import re
line = '1y2c3a'
lst = ['a', 'b', 'c']
for x in lst:
    m = re.search('\d'+x, line)
    if m:
        print m.group()

Output:

3a
2c

answered May 3, 2015 at 2:34

Stefan Pochmann

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1 Comment

Linda Over a year ago

Thanks for your assistance. New programmers are always appreciate assistance.

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