python regex trouble

Question

I have the following code :

what = re.match("get|post|put|head\s+(\S+) ",data,re.IGNORECASE)

and in the data variable let's say I have this line :

GET some-site.com HTTP/1.0 ...

If I stop the script in the debugger, and inspect the what variable, I can see it only matched GET. Why doesn't it match some-site.com ?

Answer 1

>>> re.match("(get|post|put|head)\s+(\S+) ",'GET some-site.com HTTP/1.0 ...',re.IGNORECASE).groups()
('GET', 'some-site.com')
>>>                                                                                           

Answer 2

Regex language operator precedence puts head\s+(\S+) as the 4th alternative. The parenthesis in @Mykola Kharechko's answer arrange for head as the 4th alternative, and \s+(\S+) is appended to whatever alternative matched the group.

Answer 3

+1 Mykola's answer and gimel's explanation. In addition, do you really want to use regex for this? As you've found out, they are not as straightforward as they look. Here's a non-regex-based method:

def splitandpad(s, find, limit):
    seq= s.split(find, limit)
    return seq+['']*(limit-len(seq)+1)

method, path, protocol= splitandpad(data, ' ', 2)
if method.lower() not in ('get', 'head', 'post', 'put'):
    # complain, unknown method
if protocol.lower() not in ('http/1.0', 'http/1.1'):
    # complain, unknown protocol