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performancefunctionreturn

Calling functions inside functions vs returning, which is more efficient?

In the below 2 cases, which one is more efficient?

Case 1:

def test(x):
    hello(x)

def hello(y):
    return world(y)

def world(z):
    return z

Case 2:

def test(x):
    a = hello(x)

def hello(y)
    b = world(y)
    return b

def world(z):
    c = z
    return z
Solution

  • TL;DR: both are just as fast.

    Here are the timings on my machine with the CPython 3.7.6 interpreter (on a loop of 10000000 run repeated 3 times):

    First case: 109 ns
Second case: 111 ns

    The difference is negligible between the two. Thus, the two are as fast.

    Using PyPy (JIT-based interpreter), the JIT compiler is able to optimize both cases and remove all the function calls. Thanks to the JIT, the code can be executed at a zero cost and the time of the two cases is thus exactly the same.

    If you use Cython the same kind of things could occur.

    Advice:

    Please do not tweak a Python code with micro-optimizations like this for better performance. Readability takes precedence over performance in Python.* If you really care about performance of such a thing, please use an alternative interpreter like PyPy or Cython or an integrated Python JIT compiler (such as Numba).