Bernhard Herzog wrote:
Michael Spencer <[EMAIL PROTECTED]> writes:
So, here's factorial in one line:
# state refers to list of state history - it is initialized to [1]
# on any iteration, the previous state is in state[-1]
# the expression also uses the trick of list.append() => None
# to both update the state, and return the last state
>>> [state.append(state[-1] * symbol) or state[-1]
... for symbol, state in it.izip(range(1,10),it.repeat([1]))
... ]
[1, 2, 6, 24, 120, 720, 5040, 40320, 362880]
>>>
There's no need for repeat:
[state.append(state[-1] * symbol) or state[-1]
for state in [[1]]
for symbol in range(1, 10)]
[1, 2, 6, 24, 120, 720, 5040, 40320, 362880]
While we're at it, a while back I posted a list comprehension that
implements a 'recursive' flatten:
http://groups.google.de/groups?selm=s9zy8eyzcnl.fsf%40salmakis.intevation.de
Bernhard
Much better - that also cleanly extends to any number of initializers. I also
like the approach you take in flatten (and as suggested by Carl Banks) of
putting the update mechanism in the if clause
So that gives:
def factorial(n):
return [state[-1]
for state in [[1]]
for count in xrange(1,n+1)
if state.append(state[-1] * count) or True
]
Probably of limited practical value, but fun to explore the language.
Thanks
Michael
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