python高阶函数

map

old_list = [2, 3, 4]
doubled_list = map(lambda x: x * 2, old_list)
print(list(doubled_list))  # [4, 6, 8]

product

numbers = [2, 3, 4]
summation = functools.reduce(lambda x, y: x * y, numbers)
print(summation)  # 24

filter

numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
res = list(filter(lambda x: x % 2 == 0, numbers))
print(res)  # [0, 2, 4, 6, 8]

zip

keys = ['a', 'b', 'c', 'd', 'e']
vals = [0, 1, 2, 3, 4]
res = dict(zip(keys, vals))
print(res)  # {'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4}

sort

numbers = [0, 1, 2, 3, 4]
res = sorted(numbers, reverse=True)
print(res)  # [4, 3, 2, 1, 0]

accumulate

a = [3, 4, 6, 2, 1, 9, 0, 7, 5, 8]
resutls = list(itertools.accumulate(a))
# [3, 7, 13, 15, 16, 25, 25, 32, 37, 45]
resutls = list(itertools.accumulate(a, max))
# [3, 4, 6, 6, 6, 9, 9, 9, 9, 9]
resutls = list(itertools.accumulate(a, lambda x, y: x * y))
[3, 12, 72, 144, 144, 1296, 0, 0, 0, 0]

permutations

import itertools
nums = ['a','b','c']
for num in itertools.permutations(nums):
    print(num)
# ('a', 'b')
# ('b', 'a')