Question

I’ve been wondering this for some time. As the title say, which is faster, the actual function or simply raising to the half power?

UPDATE

This is not a matter of premature optimization. This is simply a question of how the underlying code actually works. What is the theory of how Python code works?

I sent Guido van Rossum an email cause I really wanted to know the differences in these methods.

My email:

There are at least 3 ways to do a square root in Python: math.sqrt, the ‘**’ operator and pow(x,.5). I’m just curious as to the differences in the implementation of each of these. When it comes to efficiency which is better?

His response:

pow and ** are equivalent; math.sqrt doesn’t work for complex numbers, and links to the C sqrt() function. As to which one is faster, I have no idea…

Answer 1

math.sqrt(x) is significantly faster than x**0.5.

import math N = 1000000 

%%timeit for i in range(N):     z=i**.5 

10 loops, best of 3: 156 ms per loop

%%timeit for i in range(N):     z=math.sqrt(i) 

10 loops, best of 3: 91.1 ms per loop

Using Python 3.6.9 (notebook).