Python  reduce()函数的用法示例代码

from functools import reduce

from functools import reduce
# 两数相加
def add(x,y):
    return x + y
# 计算1 + 2 + 3 + ... + 100的和
sum1 = reduce(add, range(1, 101))  
print(sum1)  # 5050
# 计算列表和：1+2+3+4+5
# 使用lambda匿名函数+reduce()函数
sum2 = reduce(lambda x, y: x+y, [1,2,3,4,5])
print(sum2)  # 15
sum3 = reduce(lambda x, y: x + y, [1, 2, 3, 4, 5], 6)
# 21 = 6 + 1 + 2 + 3 + 4 + 5 
print(sum3)  # 21

from functools import reduce
lst = [1,2,3,4,5]
# 120 = 1 * 2 * 3 * 4 * 5
print(reduce(lambda x,y:x*y,lst))  # 120

from functools import reduce
str1="abcdefg"
# gfedcba
print(reduce(lambda x,y:y+x, str1))

from functools import reduce
sentences = ['Hello World!! hello Andy'] 
# 统计字符串'Hello'出现的次数
word_count =reduce(lambda a,x:a+x.count("Hello"), sentences, 0)
print(word_count)  # 1

def sum_func(arr):
    if len(arr) <= 0:
        return 0
    else:
        out = arr[0]
        for v in arr[1:]:
            out += v
        return out
a = [1, 2, 3, 4, 5]
print(sum_func(a))

from functools import reduce
a = [1, 2, 3, 4, 5]
def add(x, y): return x + y
print(reduce(add, a))

from functools import reduce
import time
def test_for(arr):
    if len(arr) <= 0:
        return 0
    out = arr[0]
    for i in arr[1:]:
        out += i
    return out
def test_reduce(arr):
    out = reduce(lambda x, y: x + y, arr)
    return out
a = [i for i in range(100000)]
t1 = time.perf_counter()
test_for(a)
t2 = time.perf_counter()
test_reduce(a)
t3 = time.perf_counter()
print('for循环耗时:', (t2 - t1))
print('reduce耗时:', (t3 - t2))