let's say I have the following code:
for a in object.a_really_huge_function():
print a
In order to prevent a_really_huge_function
from running multiple times, I am used to doing t开发者_如何学编程his in other languages:
a_list = object.a_really_huge_function()
for a in a_list:
print a
Is that necessary in Python? Will the part after in
run on every single loop?
The python interpreter is your friend.
>>> def some_func():
... print 'in some_func'
... return [1, 2, 3, 10]
...
>>> for a in some_func():
... print a
...
in some_func
1
2
3
10
In short, no, it gets called once.
You can also use generators to avoid returning huge results by relinquishing control after each step of the algorithm as follows:
def a_really_huge_fuction(huge_number):
i = 0
while i < huge_number:
yield i # Relinquishes control to caller, resume execution at next line
i = i + 1
In this case, the function is called once, but has its execution spread over huge_number
different times. See the yield documentation for more details.
It's not necessary.
for a in object.a_really_huge_function():
calls a_really_huge_function
only once.
The only advantage of saving the result in a variable would be if you are calling the same function elsewhere in your code.
If the function returns a list, you might do better in terms of memory usage by making object.a_really_huge_function()
return an iterator, but otherwise you are fine.
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