Test "while 1" vs. "while True" in Python

while_test.py

# Testing results (lower number is faster):
#                      while True            while 1
# pypy 1.7.0:          0.0733                0.0201
# cpython 2.7.1        0.146                 0.109
# cpython 3.2.2        2.79                  2.72

loops = 10000
trials = 1000

def while_True():
  x = 0
  while True:
    x += 1
    if x > loops:
      break

def while_1():
  x = 0
  while 1:
    x += 1
    if x > loops:
      break

import timeit
print('while True: ', timeit.timeit(while_True, number=trials))
print('while 1: ', timeit.timeit(while_1, number=trials))

good to know.

Turns out in Python 2, you can redefine True, so it has to do a lookup in the global namespace every time. In Python 3, True becomes a reserved word so it doesn't have to do the lookup. Thanks, /r/Python