Steven D'Aprano wrote:
> On Wed, 21 Dec 2005 16:39:19 +0100, Daniel Schüle wrote:
>
>> [EMAIL PROTECTED] wrote:
>>> How do I check if a string contains (can be converted to) an int? I
>>> want to do one thing if I am parsing and integer, and another if not.
>>>
>>> /David
>>>
>>
>> others already answered, this is just an idea
>>
>> >>> def isNumber(n):
>> ... import re
>> ... if re.match("^[-+]?[0-9]+$", n):
>> ... return True
>> ... return False
>
> This is just a thought experiment, right, to see how slow you can make
> your Python program run?
Let's leave the thought experiments to the theoretical physicists and
compare a regex with an exception-based approach:
~ $ python -m timeit -s'import re; isNumber =
re.compile(r"^[-+]\d+$").match' 'isNumber("-123456")'
1000000 loops, best of 3: 1.24 usec per loop
~ $ python -m timeit -s'import re; isNumber =
re.compile(r"^[-+]\d+$").match' 'isNumber("-123456x")'
1000000 loops, best of 3: 1.31 usec per loop
~ $ python -m timeit -s'def isNumber(n):' -s' try: int(n); return True' -s
' except ValueError: pass' 'isNumber("-123456")'
1000000 loops, best of 3: 1.26 usec per loop
~ $ python -m timeit -s'def isNumber(n):' -s' try: int(n); return True' -s
' except ValueError: pass' 'isNumber("-123456x")'
100000 loops, best of 3: 10.8 usec per loop
A tie for number-strings and regex as a clear winner for non-numbers.
Peter
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