Best way to check if string is an integer?

[Andrew Warkentin]

skanemupp at yahoo.se wrote:

>which is the best way to check if a string is an number or a char?
>could the 2nd example be very expensive timewise if i have to check a
>lot of strings?
>
>this
>
>value = raw_input()
>
>try:
>    value = int(value)
>except ValueError:
>    print "value is not an integer"
>
>
>or:
>
>
>c=raw_input("yo: ")
>if c in '0123456789':
>    print "integer"
>else:
>    print "char"
>
>
>
>or some other way?
>  
>
I always do it the first way. It is simpler, and should be faster. Also, 
the second way will only work on single-digit numbers (you would have to 
iterate over the entire string with a for loop to use it on numbers with 
more than one digit).