I'm pretty new to Python and I know Perl can do this, but I haven't found it in Python yet. What I'm trying to do is to extract a token from a line.
p = re.compile('555=\d+')
ID = p.findall(line)
where line is a single line in a file, and the digits after 555= should be recorded. However, with these two lines, I can only get things like 555=1234567, what I really want is 1234567. Can anyone help and suggest a solution? Thanks!
Use () to capture what you want:
>>> p = re.compile('555=(\d+)')
>>> p.findall("555=1234567")
['1234567']
(...)
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
You should capture the expression you want using "()".
So your expression should be p = re.compile('555=(\d+)')
searchmethod (for only one match) instead offindall(for several matches). You must put your pattern into a raw stringr'555=\d+'or escape the backslashes'555=\\d+'. If you want to only extract the value on the right, use a capture group or, why not a lookbehind (but it's slower).