Explore the relationship between Key Miss Rate and timing for Python dicts.

dict_timing.ipy

"""
Explore the relationship between Key Miss Rate and time.

i.e. if you are doing a lot of dictionary lookups, how few misses
do you need to get in order to use try/except vs methods without exceptions

run via $ ipython dict_timing.ipy
"""

def a(d, i):
    """Try / Except"""
    try:
        return d[i]
    except KeyError:
        return None
        

def b(d, i):
    """Two lookups"""
    if i in d:
        return d[i]
    return None


def c(d, i):
    """Use Get"""
    return d.get(i, None)

d, N = {}, 100

def test(n):
    global d, N
    print '%2.1f%% Miss Rate' % (100 * float(n) / N)
    
    d = {i: True for i in range(n)}
    %timeit [a(d, i) for i in range(N)]
    %timeit [b(d, i) for i in range(N)]
    %timeit [c(d, i) for i in range(N)]


def main():
    test(50)
    test(90)
    test(95)  # Break-even point

if __name__ == '__main__':
    main()