Search code examples
pythonpow

Python's POW implementation much faster than my own

I am practising the fast power algorithm in Python3, and I tested it against Python's built-in power function.

Why it turns out the built-in function is so much faster?

My code:

def levinPOW(n, k):
  res = 1
  while k:
    if k&1:
      res *= n
    n *= n
    k = k >> 1
  return res

import time
start = time.time()
a = levinPOW(2, 10000000)
end = time.time()
print(end-start)
start = time.time()
b = 2 ** 10000000
end = time.time()
print(end-start)
print(a==b)

Result:

0.31336236000061035
4.291534423828125e-06
True
Solution

  • The builtin is implemented in C which is much faster than implementing it in Python. It's also probably had several people making speed improvements to it.