import time
import re

d = re.compile(r'^[+-]?\d+$')

def is_integer_re(value):
    return d.match(value)

def is_integer(value):
    return value[0] in '+-0123456789' and all(x in '0123456789' for x in value[1:])

start = time.time()
for i in range(100000):
    is_integer_re(str(i))
print(time.time() - start)

start = time.time()
for i in range(100000):
    is_integer(str(i))
print(time.time() - start)

0.707628011703
2.40046811104