Python之内置函数

内置函数

注：查看详细https://docs.python.org/3/library/functions.html#next

 匿名函数  

def calc(x):
    return x+1


print(calc(10))
# print(lambda x:x+1)  # 匿名函数内存地址

func = lambda x: x + 1
print(func(10))

高阶函数

　　满足任意一个条件：

　　1、函数的传入参数是一个函数名

　　2、函数的返回值是一个函数名

1.map内置函数   map(func, *iterables) --> map object

num_l = [1, 2, 3, 4, 5, 6]
# lambda x: x+1


def add_one(x):
    return x+1


def map_test(func, array):
    """
    模拟map内置函数
    :param func: 传入的参数进行处理方法
    :param array: 传入可迭代的对象
    :return:
    """
    ret = []
    for i in array:
        res = func(i)
        ret.append(res)
    return ret


print(map_test(add_one, num_l))
print(map_test(lambda x: x+1, num_l))
res = map(lambda x: x+1, num_l)
print(list(res))


name = 'eric'
v = map(lambda x: x.upper(), name).__iter__()   # 把对象转成可迭代对象 遵行迭代协议
r = v.__next__()  # next直到StopIteration
print(r)

# print(list(map(lambda x: x.upper(), name)))

  2.filter函数

#!/usr/bin/env python
# -*- coding:utf-8 -*-


movie_person = ['eric_sb', 'alex_sb', 'lhf']


def sb_show(x):
    return x.endswith('_sb')


def filter_test(func, array):
    ret = []
    for p in array:
        if not func(p):
            ret.append(p)
    return ret


print(filter_test(sb_show, movie_person))

print(list(filter(lambda x: not x.endswith('_sb'), movie_person)))

  3.reduce函数

#!/usr/bin/env python
# -*- coding:utf-8 -*-


from functools import reduce

num_l = [1, 2, 3, 100]


def reduce_test(func, array, init=None):
    if init is None:
        res = array.pop(0)
    else:
        res = init
    for num in num_l:
        res = func(res, num)
    return res


# print(reduce_test(lambda x, y: x * y, num_l))
# reduce：处理一个序列，然后把序列合并操作
print(reduce(lambda x, y: x * y, num_l, 2))


def reduce(function, sequence, initial=None):  # real signature unknown; restored from __doc__
    """
    reduce(function, sequence[, initial]) -> value

    Apply a function of two arguments cumulatively to the items of a sequence,
    from left to right, so as to reduce the sequence to a single value.
    For example, reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates
    ((((1+2)+3)+4)+5).  If initial is present, it is placed before the items
    of the sequence in the calculation, and serves as a default when the
    sequence is empty.
    """
    pass

4.其它内置

#!/usr/bin/env python
# -*- coding:utf-8 -*-


# import re
# some_text = 'a,b,,,,c d'
# reObj = re.compile('[, ]+')  创建re对象
# print(reObj.split(some_text))


import re

some_text = 'a,b,,,,c d'
print(re.split('[, ]+', some_text))  # 会导致重复re模块，降低匹配速度
print(complex('1+2j'))

# print(complex('1 + 2j')) ValueError官方文档上
exec("print("hello, world")")
print(eval("1+2*2"))
a = '{"name":"alex"}'
print(eval(a))
print(float(2))
print(help(compile))
print(repr(1))  # 终端打开
# slice() 切片
# vars() 有点像locals()