Best way to check if string is an integer?

[skanemupp at yahoo.se]

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?