re.findall not returning full match?

Question

I have a file that includes a bunch of strings like \"size=XXX;\". I am trying python\'s re module for the first time and am a bit mystified by the following behavior: if I

Answer 1

When a regular expression contains parentheses, they capture their contents to groups, changing the behaviour of findall() to only return those groups. Here's the relevant section from the docs:

(...)

Matches whatever regular expression is inside the parentheses, and indicates the start and end of a group; the contents of a group can be retrieved after a match has been performed, and can be matched later in the string with the \number special sequence, described below. To match the literals '(' or ')', use \( or \), or enclose them inside a character class: [(] [)].

To avoid this behaviour, you can use a non-capturing group:

>>> print re.findall(r'size=(?:50|51);',myfile)
['size=51;', 'size=51;', 'size=51;', 'size=50;', 'size=50;', 'size=50;', 'size=50;']

Again, from the docs:

(?:...)

A non-capturing version of regular parentheses. Matches whatever regular expression is inside the parentheses, but the substring matched by the group cannot be retrieved after performing a match or referenced later in the pattern.