In Python, I often hear that it is better to "beg forgiveness" (exception catching) instead of "ask permission" (type/condition checking). In regards to enforcing duck typing in Python, is this

try:
    x = foo.bar
except AttributeError:
    pass
else:
    do(x)

better or worse than

if hasattr(foo, "bar"):
    do(foo.bar)
else:
    pass

in terms of performance, readability, "pythonic", or some other important factor?