在python正则表达式中匹配表达式

Question

I'm trying to match a coordinate with a python string regex, but I'm not getting a result. I was to see if the input is a valid coordinate definition but I'm not getting the correct match using the code below. Can someone tell me what's wrong?

def coordinate(coord):
     a = re.compile("^(([0-9]+), ([0-9]+))$")
     b = a.match(coord)
     if b:
         return True
     return False

Currently, it's returning false even if I pass in (3, 4) which is a valid coordinate.

Answer 1

This works:

from re import match
def coordinate(coord):   
    return bool(match("\s*\(\s*-?\d+(?:\.\d+)?\s*,\s*-?\d+(?:\.\d+)?\s*\)\s*$", coord))

It is also quite powerful, having the ability to handle negative numbers, fractions, and an optional space between the numbers.

Below is a breakdown of the Regex pattern:

\s*         # Zero or more whitespace characters
\(          # An opening parenthesis
\s*         # Zero or more whitespace characters
-?          # An optional hyphen (for negative numbers)
\d+         # One or more digits
(?:\.\d+)?  # An optional period followed by one or more digits (for fractions)
\s*         # Zero or more whitespace characters
,           # A comma
\s*         # Zero or more whitespace characters
-?          # An optional hyphen (for negative numbers)
\d+         # One or more digits
(?:\.\d+)?  # An optional period followed by one or more digits (for fractions)
\s*         # Zero or more whitespace characters
\)          # A closing parenthesis
\s*         # Zero or more whitespace characters
$           # End of the string

Answer 2

You need to escape the parentheses that you are trying to match. Try using the following:

^(\([0-9]+,\s[0-9]+\))$

Answer 3

It seems to me that you do not properly escape the parenthesis that makes the coordinate syntax. In regex, parenthesis are special characters used for grouping and capturing . You need to escape them this way:

>>> a = re.compile("^\(([0-9]+), ([0-9]+)\)$")
>>> a.match("(3, 4)")
<_sre.SRE_Match object at 0x0000000001D91E00>