[SOLVED] Does python cache items in the same line and use again later

Does python cache items in the same line and use again later

With this line:

print(sum(tuple), len(tuple), sum(tuple)/len(tuple))

Will python cache sum(tuple) in the 0 index and use it in the average calculation (2 index)?

Or will with calculate sum(tuple) again?

Solution

Python won't perform this optimization for you. You can see this by defining your own function instead of sum and observing the side effect:

import functools

def my_sum(x):
    print('my sum')
    return functools.reduce(lambda a, b: a + b, x)

tup = (1, 2, 3)
print(my_sum(tup), len(tup), my_sum(tup)/len(tup))

If you run this snippet, you'll see the phrase "my sum" printed twice, proving the call to my_sum isn't optimized out.

Having said that, you could implement this optimization yourself by using functools' cache:

import functools

@functools.cache
def my_sum(x):
    print('my sum')
    return functools.reduce(lambda a, b: a + b, x)

tup = (1, 2, 3)
print(my_sum(tup), len(tup), my_sum(tup)/len(tup))

(or by using the := operator as Andrej Kesely suggests in the comments)