python学习day-5 变量与递归函数

一、局部变量与全局变量

name='lhf'             全局变量


def change_name():
    global name        全局变量   不加global就是局部变量
    name='帅了一比'
    print('change_name',name)


change_name()
print(name)

name='lhf'

def change_name():
    name1='帅了一比'
    name2='帅了一比'
    name3='帅了一比'
    print('change_name',name)

globals关键字

NAME = "杠"

def yangjian():
    global NAME
    NAME = "小东北"
    print('我要搞', NAME)

def qupengfei():
    print('我要搞', NAME)

yangjian()
qupengfei()
--------------------------------------------------


NAME = "产品经理"

def yangjian():
    # NAME = "史正文"
    global NAME # 已经声明，ＮＡＭＥ就是全局的的那个变量
    print('我要搞', NAME)
    NAME = "小东北"  # 修改 全局的变量
    print('我要搞', NAME)

def qupengfei():
    NAME = "基"
    print('我要搞', NAME)

如果函数的内容无global关键字，
  - 有声明局部变量
        NAME = ["产品经理","廖波湿"]
        def qupengfei():
            NAME = "自己"
            print('我要搞', NAME)
        qupengfei()
  - 无声明局部变量
        NAME = ["产品经理","廖波湿"]
        def qupengfei():
            NAME.append('XXOO')
            print('我要搞', NAME)
        qupengfei()

如果函数的内容有global关键字
  - 有声明局部变量
        NAME = ["产品经理","廖波湿"]
        def qupengfei():
            global NAME
            NAME = "自己"
            print('我要搞', NAME)
        qupengfei()
        错误示例
        NAME = ["产品经理","廖波湿"]
        def qupengfei():
            NAME = "自己"
            global NAME
            print('我要搞', NAME)
        qupengfei()
  - 无声明局部变量
        NAME = ["产品经理","廖波湿"]
        def qupengfei():
            global NAME
            NAME = ["阿毛"]
            NAME.append('XXOO')
            print('我要搞', NAME)
        qupengfei()

####### 全局变量变量名大写
####### 局部变量变量名小写


优先读取局部变量，能读取全局变量，无法对全局变量重新赋值 NAME=“fff”，但是对于可变类型，可以对内部元素进行操作
如果函数中有global关键字，变量本质上就是全局的那个变量，可读取可赋值 NAME=“fff”





NAME = '海风'

def huangwei():
    name = "黄伟"
    print(name)
    def liuyang():
        name = "刘洋"
        print(name)
        def nulige():
            name = '沪指花'
            print(name)
        print(name)
        nulige()
    liuyang()
    print(name)

huangwei()

name = "刚娘"

def weihou():
    name = "陈卓"
    def weiweihou():
        nonlocal name   # nonlocal，指定上一级变量，如果没有就继续往上直到找到为止
        name = "冷静"

    weiweihou()
    print(name)

print(name)
weihou()
print(name)








二、前向引用

实例一：报错
def foo():
    print('from foo')
    bar()

foo()
实例2
def bar():
    print('from bar')
def foo():
    print('from foo')
    bar()

foo()


实例3
def foo():
    print('from foo')
    bar()

def bar():
    print('from bar')
foo()
实例4：报错
def foo():
    print('from foo')
    bar()

foo()

def bar():
    print('from bar')

三、递归 

1
def calc(n):
    print(n)
    if int(n / 2) == 0:
        return n
    res=calc(int(n / 2))
    return res



2

import time

person_list = ['alex', 'wupeiqi', 'linhaifeng', 'zsc']


def ask_way(person_list):
    print('-' * 60)
    if len(person_list) == 0:
        return '根本没人知道'
    person = person_list.pop(0)
    if person == 'linhaifeng':
        return '%s说:我知道,老男孩就在沙河汇德商厦,下地铁就是' % person

    print('hi 美男[%s],敢问路在何方' % person)
    print('%s回答道:我不知道,但念你慧眼识猪,你等着,我帮你问问%s...' % (person, person_list))
    time.sleep(1)
    res = ask_way(person_list)

    print('%s问的结果是: %res' % (person, res))
    return res


res = ask_way(person_list)
print(res)