Python regular expressions – how to capture multiple groups from a wildcard expression?
Question:
I have a Python regular expression that contains a group which can occur zero or many times – but when I retrieve the list of groups afterwards, only the last one is present. Example:
re.search("(w)*", "abcdefg").groups()
this returns the list (‘g’,)
I need it to return (‘a’,’b’,’c’,’d’,’e’,’f’,’g’,)
Is that possible? How can I do it?
Answers:
re.findall(r"w","abcdefg")
In addition to Douglas Leeder’s solution, here is the explanation:
In regular expressions the group count is fixed. Placing a quantifier behind a group does not increase group count (imagine all other group indexes increment because an eralier group matched more than once).
Groups with quantifiers are the way of making a complex sub-expression atomic, when there is need to match it more than once. The regex engine has no other way than saving the last match only to the group. In short: There is no way to achieve what you want with a single “unarmed” regular expression, and you have to find another way.
I have a Python regular expression that contains a group which can occur zero or many times – but when I retrieve the list of groups afterwards, only the last one is present. Example:
re.search("(w)*", "abcdefg").groups()
this returns the list (‘g’,)
I need it to return (‘a’,’b’,’c’,’d’,’e’,’f’,’g’,)
Is that possible? How can I do it?
re.findall(r"w","abcdefg")
In addition to Douglas Leeder’s solution, here is the explanation:
In regular expressions the group count is fixed. Placing a quantifier behind a group does not increase group count (imagine all other group indexes increment because an eralier group matched more than once).
Groups with quantifiers are the way of making a complex sub-expression atomic, when there is need to match it more than once. The regex engine has no other way than saving the last match only to the group. In short: There is no way to achieve what you want with a single “unarmed” regular expression, and you have to find another way.