Python: How long does it take to remove a key from a dict?

I try to do micro-benchmarks in python as little as possible, but it never hurts to be aware of the cost of your primitive operations. That's regardless of the language you're coding in.

So, today's experiment... Say you want to remove a key from a dict whether it exists or not. How long does it take? Depends on your method of choice...

pop: 0.24 usec/pass
try/except: 2.27 usec/pass
if in: 0.11 usec/pass
if has_key: 0.20 usec/pass

if x in d: del d[x] wins for execution time, but there are definitely times when the (almost 20x!) overhead of exception can be worth it.

import timeit
num = 10000

a = {}

setup = """
a = {}
"""
stmt = """
a.pop("hi", None)
"""
t = timeit.Timer(stmt=stmt, setup=setup)
print "pop: %.2f usec/pass" % (1000000 * t.timeit(number=num)/num)

stmt = """
try:
  del a['hi']
except KeyError:
  pass
"""
t = timeit.Timer(stmt=stmt, setup=setup)
print "try/except: %.2f usec/pass" % (1000000 * t.timeit(number=num)/num)

stmt = """
if 'hi' in {}:
  del a['hi']
"""
t = timeit.Timer(stmt=stmt, setup=setup)
print "if in: %.2f usec/pass" % (1000000 * t.timeit(number=num)/num)

stmt = """
if {}.has_key('hi'):
  del a['hi']
"""
t = timeit.Timer(stmt=stmt, setup=setup)
print "if has_key: %.2f usec/pass" % (1000000 * t.timeit(number=num)/num)