def cal(n):print(n)if n > 0:return cal(int(n/2))else:return 'n=0 done'print(cal(10))输出：
10
5
2
1
0
n=0 done

通过层层调用，达到条件后，结束调用，再层层返回。

给定一个节点，在menus找到他，如果该节点存在，打印出来，并返回true，如果不存在，就返回false

menus = [    {        'text': '北京',        'children':[             {'text':'昌平','children':[                {'text':'沙河','children':[]}             ]}]}]

def find_menu(menu,city):    if menu:        for i in menu:            if i['text'] != city:               return find_menu(i['children'],city)  #如果本层没有city，则会深入到下一层            else:                print(city)                return True    else:        return False

city=input('>>>>')print(find_menu(menus,city))

可以看到比较容易就实现了。

menus = [{'text': '北京','children':[{'text':'朝阳','children':[]},{'text':'昌平','children':[{'text':'沙河','children':[]},{'text':'回龙观','children':[]},]},]},{'text':'上海','children':[{'text':'宝山','children':[]},{'text':'金山','children':[]}]}
]

def find_menu(menu,city):if menu:for i in menu:if i['text'] != city:return find_menu(i['children'],city)  #如果本层没有city，则会深入到下一层else:print(city)return Trueelse:return False
city=input('>>>>')
print(find_menu(menus,city))>>>>朝阳
朝阳
True>>>>沙河
False>>>>宝山
False

def find_menu(city,menu):if menu:for i in menu:if i['text'] != city:flag=find_menu(city,i['children'])if flag==True:return Trueelse:print(city)return Trueelse:return Falseelse:return False        

def find_menu(city,menu):if menu:for i in menu:if i['text'] != city:if find_menu(city,i['children']):return Trueelse:print(city)return Trueelse:return False