Why use regex finditer() rather than findall()

Question

What is the advantage of using finditer() if findall() is good enough? findall() returns all of the matches while finditer() returns match object which can't be processed as directly as a static list.

For example:

import re
CARRIS_REGEX = (r'<th>(\d+)</th><th>([\s\w\.\-]+)</th>'
                r'<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)

Output:

<_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')

I ask this out of curiosity.

Answer 1

Sometimes it's superfluous to retrieve all matches. If the number of matches is really high you could risk filling up your memory loading them all.

Using iterators or generators is an important concept in modern python. That being said, if you have a small text (e.g this web page) the optimization is minuscule.

Here is a related question about iterators: Performance Advantages to Iterators?