Zen of Python
> There should be one-- and preferably only one --obvious way to do it.
> Although that way may not be obvious at first unless you're Dutch.
> There should be one-- and preferably only one --obvious way to do it.
> Although that way may not be obvious at first unless you're Dutch.
def factorial(n):
result = 1
for i in range(2, n + 1):
result *= i
return result
def factorial(n):
if n == 0 or n == 1:
return 1
else:
return n * factorial(n - 1)
In my opinion, it's great that there are such few options to express this operation, and that both cases are eminently readable.
There are lots of ways to do this in Python. That's not only fine, it's inevitable.
Here's a burnt-out PhD level one using highly pythonic paradigms:
def fac(n):
return eval("*".join(str(1+a) for a in range(n))Of course there are more ways, but I would definitely qualify this as "unreasonably convoluted".
Again I ask, considered by who? This is the kind of language that wikipedians would call "weasel words". Of course you shouldn't misuse eval or goto, and it's fine to have a rule of thumb to discourage it.
What's not fine, and strikes me as no better than superstition, is to make vague "everybody knows"-type statements that convey almost no information. If it's bad you should be able to say (or provide reference to) specifically how it's bad and what convinced you this was the case.
And yes, I deliberately wrote a perverse function because it was funny, but if you did a real fold instead of my fake one with strings then it wouldn't be so perverse. And wasn't it more pythonic to use a generator?
Not embracing Perl's tmtowtdi is fine, but until you solve the halting problem some people will write "x+x" and some will write "2*x" and some will write "x<<2" and those can't sensibly be unified.
Your idiomatic Python version uses three variables, two of which mutate. I'm a simple man - go easy on me please! The `n + 1` took me a while to figure out too.
from math import prod # from Python 3.8 onwards
def factorial(n):
return prod(range(n+1)) return prod(1,range(n+1))Edit: prod(range(1, n+1)) does work
This is exactly why I asked the question!