Using anchors in python regex to get exact match

Question

I need to validate a version number consisting of 'v' plus positive int, and nothing else eg "v4", "v1004"

I have

import re
pattern = "\Av(?=\d+)\W"

m = re.match(pattern, "v303")
if m is None:
    print "noMatch"
else:
    print "match"

But this doesn't work! Removing the \A and \W will match for v303 but will also match for v30G, for example

Thanks

Answer 1

Pretty straightforward. First, put anchors on your pattern:

"^patternhere$"

Now, let's put together the pattern:

"^v\d+$"

That should do it.

Answer 2

I think you may want \b (word boundary) rather than \A (start of string) and \W (non word character), also you don't need to use lookahead (the (?=...)).

Try: "\bv(\d+)" if you need to capture the int, "\bv\d+" if you don't.

Edit: You probably want to use raw string syntax for Python regexes, r"\bv\d+\b", since "\b" is a backspace character in a regular string.

Edit 2: Since + is "greedy", no trailing \b is necessary or desired.

Answer 3

Simply use

 \bv\d+\b

Or enclosed it with ^\bv\d+\b$

to match it entirely..