python实用小技巧之装饰器

python的装饰器：

假设我们要给很多函数统计函数运行时间，一般情况我们会给每个函数做如下处理：

import time

def fun()
	t1 = time.time()
	函数体...
	t2 = time.time()
	print(t2-t1)

如果加上装饰器以后就不需要每个函数都做上面的处理。

import time

def show_distance_time(func):
    def wrapper(*args):
        t1 = time.time()
        res = func(*args)
        t2 = time.time()
        print(func.__name__, "time", t2 - t1 )
        return res
    return wrapper

# 判断该数是否为质数
def is_prime(num):
    if num < 2 : return False
    if num == 2 : return True
    mid = int(num**(0.5))
    for i in range(2, mid + 1):
        if num % i == 0:
            return False
    return True

# 统计start到end之间质数的个数
@show_distance_time
def count_prime_nums(start, end):
    if start > end : return 0
    count = 0
    for i in range(start, end+1):
        if is_prime(i):
            count += 1
    return count

# 求1到end的和
@show_distance_time
def sum_until(end):
    sum1 = 0
    for i in range(end):
        sum1 += i
    return sum1

if __name__ == "__main__":
    count_prime_nums(1, 200000)
    sum_until(200000)
    
output:
count_prime_nums time 0.33507466316223145
sum_until time 0.006981849670410156