forgivness vs. permission

gistfile1.txt

In [4]: def forgiveness(x):
    try:                     
        x.plugins.append(1)
    except AttributeError:
        x.plugins = [1]
   ...:         

In [5]: def permission(x):
    if not hasattr(x, 'plugins'):
        x.plugins = []
    x.plugins.append(1)
   ...:     

In [6]: class X(object):
   ...:     pass
   ...: 

In [7]: x = X()

In [8]: %timeit forgiveness(x)
1000000 loops, best of 3: 233 ns per loop

In [9]: %timeit permission(x)

1000000 loops, best of 3: 333 ns per loop

In [10]: 

In [10]: x.plugins = []

In [11]: %timeit forgiveness(x)
1000000 loops, best of 3: 232 ns per loop

In [12]: %timeit permission(x)
1000000 loops, best of 3: 331 ns per loop