try / except is slllloooooowwwww for key checking. use the built in membership test instead.

exceptionprofile.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#

import timeit
import string
import pprint

def exfn(d_in, key):
    try:
        d_in[key]
    except KeyError:
        return False
    return True

def iffn(d_in, key):
    if key in d_in:
        return True
    return False

dict_arg = {s:ord(s) for s in string.printable}
times = {
    'ex_raised': timeit.timeit('exfn({0}, "poop")'.format(dict_arg), 
        setup="from __main__ import exfn"),
    'ex_found': timeit.timeit('exfn({0}, "D")'.format(dict_arg), 
        setup="from __main__ import exfn"),
    'if_notfound': timeit.timeit('iffn({0}, "poop")'.format(dict_arg), 
        setup="from __main__ import iffn"),
    'if_found': timeit.timeit('iffn({0}, "E")'.format(dict_arg), 
        setup="from __main__ import iffn")
    }

pprint.pprint(times)