问题
So doing this (in python 3.7.3):
>>> from re import findall
>>> s = '7.95 + 10 pieces'
>>> findall(r'(\d*\.)?\d+', s)
['7.', ''] # Expected return: ['7.95', '10']
I'm not sure why it doesn't find all the floats inside? Is this possibly some python quirk about capturing groups?
My logic behind the regex:
(\d*\.)? matches either 1 or none of any number of digits, followed by a period.
\d+ then maches any number of digits, so this regex should match any of 11.11, 11, .11 and so on. Whats wrong here?
回答1:
As you guessed correctly, this has to do with capturing groups. According to the documentation for re.findall:
If one or more groups are present in the pattern, return a list of groups
Therefore, you need to make all your groups () non-capturing using the (?:) specifier. If there are no captured groups, it will return the entire match:
>>> pattern = r'(?:\d*\.)?\d+'
>>> findall(pattern, s)
['7.95', '10']
来源：https://stackoverflow.com/questions/59745069/regex-behaving-weird-when-finding-floating-point-strings