DAY11 函数进阶（函数名的本质，闭包，迭代器）

#一。 函数名表示函数的内存地址
def func():
    print(111)
print(func)     
>>><function func at 0x00000199DFD22F28>

#二。函数名可以赋值给变量,可以作为容器数据类型的元素。

def func():
    print(111)
f = func      #2.函数名可以赋值给一个变量
f()
>>>
111

def foo1():
    print(1)
def foo2():
    print(2)
def foo3():
    print(3)
def foo4():
    print(4)

l1 = [foo1,foo2,foo3,foo4] #3.函数名可以当做容器类数据类型的元素
for i in l1:
    i()
>>>
1
2
3
4

#三。函数名可以作为参数传递给函数
def fun1():
    print(222)
def func2(x):
    x()
func2(fun1)
>>>
222

#四。函数名可以作为函数的返回值
def func1(x):
    return x       
def func2():
    print(‘in the func2‘)
res = func1(func2)
res()

#这是闭包
def wrapper(x):
    def inner():
        print(x)
    inner()
wrapper(‘he‘)
>>>
‘he‘


#这是闭包
name = ‘he‘
def wrapper(n):     
    def inner():
        print(n)
    return inner()
wrapper(name)

##这不是闭包
name = ‘he‘
def wrapper():
    def inner():
        print(name)     #因为引用了全局作用域的变量
    return inner()
wrapper()

# 这是闭包,返回有cell就是闭包
def func():
    name = ‘he‘
    def inner():
        print(name)
    print(inner.__closure__)
    inner()
func()
>>>
(<cell at 0x00000183451865E8: str object at 0x0000018345217810>,)
he


#这不是闭包，因为返回的是None
name = ‘he‘
def wrapper():
    def inner():
        print(name)
    print(inner.__closure__)
    inner()
wrapper()
>>>
None
he

‘‘‘闭包嵌套‘‘‘
def wrapper():
    money = 1000
    def func():
        name = ‘he‘
        def inner():
            print(name + ‘ have ‘ + str(money))
        return inner
    return func

f = wrapper()
i = f()
i()

#回顾我们学过的可迭代对象：str,list,tuple,dict,set,range()
# dir(obj) 方法：返回一个对象的所有方法

s1 = ‘str‘
print(dir(s1))    #返回了字符串的所有方法
>>>       
[‘__add__‘, ‘__class__‘, ‘__contains__‘, ‘__delattr__‘, ‘__dir__‘, ‘__doc__‘, ‘__eq__‘, ‘__format__‘, ‘__ge__‘, ‘__getattribute__‘, ‘__getitem__‘, ‘__getnewargs__‘, ‘__gt__‘, ‘__hash__‘, ‘__init__‘, ‘__init_subclass__‘, ‘__iter__‘, ‘__le__‘, ‘__len__‘, ‘__lt__‘, ‘__mod__‘, ‘__mul__‘, ‘__ne__‘, ‘__new__‘, ‘__reduce__‘, ‘__reduce_ex__‘, ‘__repr__‘, ‘__rmod__‘, ‘__rmul__‘, ‘__setattr__‘, ‘__sizeof__‘, ‘__str__‘, ‘__subclasshook__‘, ‘capitalize‘, ‘casefold‘, ‘center‘, ‘count‘, ‘encode‘, ‘endswith‘, ‘expandtabs‘, ‘find‘, ‘format‘, ‘format_map‘, ‘index‘, ‘isalnum‘, ‘isalpha‘, ‘isdecimal‘, ‘isdigit‘, ‘isidentifier‘, ‘islower‘, ‘isnumeric‘, ‘isprintable‘, ‘isspace‘, ‘istitle‘, ‘isupper‘, ‘join‘, ‘ljust‘, ‘lower‘, ‘lstrip‘, ‘maketrans‘, ‘partition‘, ‘replace‘, ‘rfind‘, ‘rindex‘, ‘rjust‘, ‘rpartition‘, ‘rsplit‘, ‘rstrip‘, ‘split‘, ‘splitlines‘, ‘startswith‘, ‘strip‘, ‘swapcase‘, ‘title‘, ‘translate‘, ‘upper‘, ‘zfill‘]

# 方法一：通过对象是否含有‘__iter__’方法
dic = {‘name‘:‘he‘,‘age‘:23}
print(‘__iter__‘ in dir(dic))
>>>
True


# 方法二：通过isinstance()方法判断

from collections import Iterable
dic = {‘name‘:‘he‘,‘age‘:23}
print(isinstance(dic,Iterable))
>>>
True

#我们接触过得迭代器有：文件句柄

# 方法一：判断对象的方法中是否同时含有"__iter__"和"__next__"
f = open(r‘E:\python_training_s1\day9\register.txt‘,encoding=‘utf-8‘)
print(‘__iter__‘ in dir(f))
print(‘__next__‘ in dir(f))
f.close()
>>>
True
True

#方法二：使用isinstance（obj,Iterator）,返回True/False

from collections import Iterator
f = open(r‘E:\python_training_s1\day9\register.txt‘,encoding=‘utf-8‘)
print(isinstance(f,Iterator))
f.close()
>>>
True

l1 = [1,2,3] #可迭代对象
iter_l1 = l1.__iter__()  #迭代器 iter(iterable_obj)
print(iter_l1,type(iter_l1))

print(iter_l1.__next__())
print(iter_l1.__next__())
print(iter_l1.__next__())

# 使用while循环重现for循环的原理

s1 = ‘abcd‘
iter1 = s1.__iter__()
while 1:
    try:
        print(iter1.__next__())
    except Exception:
        break