Python 代码在函数中运行得更快的原因解析

def hello_world():
    print("Hello, World!")
import dis
dis.dis(hello_world)

def my_function():
    for i in range(100000000):
        pass

  SETUP_LOOP              20 (to 23)
  LOAD_GLOBAL             0 (range)
  LOAD_CONST              3 (100000000)
  CALL_FUNCTION           1
  GET_ITER            
  FOR_ITER                6 (to 22)
  STORE_FAST              0 (i)
  JUMP_ABSOLUTE           13
  POP_BLOCK           
  LOAD_CONST              0 (None)
  RETURN_VALUE

for i in range(100000000):
	pass

  SETUP_LOOP              20 (to 23)
  LOAD_NAME               0 (range)
  LOAD_CONST              3 (100000000)
  CALL_FUNCTION           1
  GET_ITER            
  FOR_ITER                6 (to 22)
  STORE_NAME              1 (i)
  JUMP_ABSOLUTE           13
  POP_BLOCK           
  LOAD_CONST              2 (None)
  RETURN_VALUE

def factorial(n):
    result = 1
    for i in range(1, n + 1):
        result *= i
    return result

n = 20
result = 1
for i in range(1, n + 1):
    result *= i

import timeit
# 函数
def benchmark():
    start = timeit.default_timer()
    factorial(20)
    end = timeit.default_timer()
    print(end - start)
benchmark()
# Prints: 3.541994374245405e-06
# 全局范围
start = timeit.default_timer()
n = 20
result = 1
for i in range(1, n + 1):
    result *= i
end = timeit.default_timer()
print(end - start) 
# Pirnts: 5.375011824071407e-06

import cProfile
def sum_of_squares():
    total = 0
    for i in range(1, 10000000):
        total += i * i
i = None
total = 0
def sum_of_squares_g():
    global i
    global total
    for i in range(1, 10000000):
        total += i * i
def profile(func):
    pr = cProfile.Profile()
    pr.enable()
    func()
    pr.disable()
    pr.print_stats()
#
# Profile function code
#
print("Function scope:")
profile(sum_of_squares)
#
# Profile global scope code
#
print("Global scope:")
profile(sum_of_squares_g)

Function scope:
         2 function calls in 0.903 seconds
   Ordered by: standard name
   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
   1       0.903    0.903    0.903    0.903 profiler.py:3(sum_of_squares)
   1       0.000    0.000    0.000    0.000 {method 'disable' of '_lsprof.Profiler' objects}
Global scope:
         2 function calls in 1.358 seconds
   Ordered by: standard name
   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
   1       1.358    1.358    1.358    1.358 profiler.py:10(sum_of_squares_g)
   1       0.000    0.000    0.000    0.000 {method 'disable' of '_lsprof.Profiler' objects}