forward reference前向引用，gloal values and local values全局变量和局部变量，recursive function递归函数

1.全局变量与局部变量练习

 1 # -*- coding: UTF-8 -*-
 2 def bar():
 3     print('from bar')
 4 def foo():
 5     print('from foo')
 6     bar()
 7 foo()
 8
 9 name = 'lhf'
10 def change_name():
11     global name
12     name = 'such a good young boy'
13     print('change_name',name)
14 def change_name1():
15     name1 = '帅了一比'
16     name2 = '帅了一比'
17     name3 = '帅了一比'
18     print('change_name',name)
19 change_name()
20 change_name1()
21 print(name)
22
23 NAME = '杠娘'
24 def yangjian():
25     global NAME
26     NAME = 'a cute little northwestern man'
27     print('i am going to hang out with ' + NAME)
28 def qupengfei():
29     NAME = 'alex'
30     print('i am going to hang out with ' + NAME)
31 yangjian()
32 qupengfei()
33
34 NAME = ['a','b']
35 def qupengfei():
36     NAME = 'myself'
37     print('i am fucking ' + NAME)
38 qupengfei()
39
40 NAME = ['c','d']
41 def yuyukun():
42     NAME.append('e')
43     print('i am fucking',NAME)
44 yuyukun()
45
46 result:
47 from foo
48 from bar
49 ('change_name', 'such a good young boy')
50 ('change_name', 'such a good young boy')
51 such a good young boy
52 i am going to hang out with a cute little northwestern man
53 i am going to hang out with alex
54 i am fucking myself
55 ('i am fucking', ['c', 'd', 'e'])

2.全局变量与局部变量 例子

#global keywork
name = '刚娘'
def weihou():
    name = '陈卓'
    def weiweihou():
        global name #此处全局变量对应line780,表示重申变量name为全局变量
        name = '冷静' #此处name仅为weiweihou()中的全局变量
    weiweihou()
    print(name) #此时打印的name对应'陈卓'，因为weihou()中声明了name='陈卓'的局部变量
print(name)
weihou()
print(name)
#nonlocal keywork
name = '刚娘'
def weihou():
    name = '陈卓'
    def weiweihou():
        nonlocal name #修改上级变量，陈卓改为冷静
        name = '冷静'
    weiweihou()
    print(name)
print(name)
weihou()
print(name)

result:
刚娘
陈卓
冷静

刚娘
冷静
刚娘

3.累加的递归练习

def add(n):
    print(n)
    if n == 1:
        return n
    else:
        return (n + add(n-1))
res = add(10)
print(res)

result:
10
9
8
7
6
5
4
3
2
1
55

4.公因子的递归练习

    print(n)
    if int(n / 2) == 0:
        return n
    res = calc(int(n/2))
    return res
res = calc(10)
print(res)

5.问路的递归练习

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，但念你慧眼识珠，你等着，我帮你问问%s...'%(person,person_list))
    # time.sleep(10)
    res = ask_way(person_list)
    print('%s问的结果是：%res'%(person,res))
    return res
res = ask_way(person_list)
print(res)