Python Tips

Python Tips

1、float转int，取整除比强转更快

测试代码：

import time

iter_num = 10000000
t1 = time.time()
for a in range(iter_num):
    2.3//1
t2 = time.time()
for b in range(iter_num):
    int(2.3)
t3 = time.time()

print(t2-t1)
print(t3-t2)

测试结果：

0.4637594223022461
1.7513151168823242

2、递归函数装饰lru_chache()性能惊人

测试代码：

import functools
import time

@functools.lru_cache()
def fib(n):
    return n if n < 2 else fib(n-1)+fib(n-2)

def fib_(n):
    return n if n < 2 else fib_(n-1)+fib_(n-2)

t1 = time.time()
fib(30)
t2 = time.time()
fib_(30)
t3 = time.time()

print(t2-t1)
print(t3-t2)

测试结果：

0.0
5.077128887176514

原因：lru_cache()将相同参数的函数值记录下来，而避免重复计算。