Python – Difference Between re.search() and re.findall()

pythonregex

The following code is very strange:

 >>> words = "4324324 blahblah"
 >>> print re.findall(r'(\s)\w+', words)
 [' ']
 >>> print re.search(r'(\s)\w+', words).group()
 blahblah

The () operator seems to behave poorly with findall. Why is this? I need it for a csv file.

Edit for clarity: I want to display blahblah using findall.

I discovered that re.findall(r'\s(\w+)', words) does what I want, but have no idea why findall treats groups in this way.

Best Answer

One character off:

>>> print re.search(r'(\s)\w+', words).groups()
(' ',)
>>> print re.search(r'(\s)\w+', words).group(1)
' '

findall returns a list of all groups captured. You're getting a space back because that's what you capture. Stop capturing, and it works fine:

>>> print re.findall(r'\s\w+', words)
[' blahblah']

Use the csv module

Related Solutions

Python Regex – Different Behavior Between re.finditer and re.findall

I can't reproduce this here. Have tried it with both Python 2.7 and 3.1.

One difference between finditer and findall is that the former returns regex match objects whereas the other returns a tuple of the matched capturing groups (or the entire match if there are no capturing groups).

import re
CARRIS_REGEX=r'<th>(\d+)</th><th>([\s\w\.\-]+)</th><th>(\d+:\d+)</th><th>(\d+m)</th>'
pattern = re.compile(CARRIS_REGEX, re.UNICODE)
mailbody = open("test.txt").read()
for match in pattern.finditer(mailbody):
    print(match)
print()
for match in pattern.findall(mailbody):
    print(match)

prints

<_sre.SRE_Match object at 0x00A63758>
<_sre.SRE_Match object at 0x00A63F98>
<_sre.SRE_Match object at 0x00A63758>
<_sre.SRE_Match object at 0x00A63F98>
<_sre.SRE_Match object at 0x00A63758>
<_sre.SRE_Match object at 0x00A63F98>
<_sre.SRE_Match object at 0x00A63758>
<_sre.SRE_Match object at 0x00A63F98>

('790', 'PR. REAL', '21:06', '04m')
('758', 'PORTAS BENFICA', '21:10', '09m')
('790', 'PR. REAL', '21:14', '13m')
('758', 'PORTAS BENFICA', '21:21', '19m')
('790', 'PR. REAL', '21:29', '28m')
('758', 'PORTAS BENFICA', '21:38', '36m')
('758', 'SETE RIOS', '21:49', '47m')
('758', 'SETE RIOS', '22:09', '68m')

If you want the same output from finditer as you're getting from findall, you need

for match in pattern.finditer(mailbody):
    print(tuple(match.groups()))

Best Answer

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Python Regex – Different Behavior Between re.finditer and re.findall

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