# 函數(shù)是對象：支持賦值操作。
def test1(n):
    print(f"hello, {n}!")

# test1的函數(shù)名賦值給 new1
new1 = test1
new1("tom") # hello, tom!

# 函數(shù)可以刪除
def test2(n):
    print(f"hello, {n}!")
del test2
# test2("tom") # NameError: name 'test2' is not defined

# 函數(shù)名字和函數(shù)本身完全是分開的：刪除test3，不影響已經(jīng)賦值的調(diào)用
def test3(n):
    print(f"hello, {n}!")

new3 = test3
del test3
new3("Jam") # hello, Jam!

# 函數(shù)因?yàn)槭菍ο螅涂梢越Y(jié)合數(shù)據(jù)結(jié)構(gòu)使用
def test4(n):
    print(f"hello, {n}!")

data = [1, "a", {"name": "tom"}, test4]
for i in data:
    from types import FunctionType
    if type(i) == FunctionType:
        test4("Lily")  # hello, Lily!

# 函數(shù)因?yàn)槭菍ο?，就可以作為函?shù)參數(shù)
def test5(n):
    print("原始函數(shù)執(zhí)行")
    print(f"hello, {n}")

def new5(n):
    n("Golang")

new5(test5)  # 原始函數(shù)執(zhí)行  hello, Golang

# 函數(shù)因?yàn)槭菍ο?，可以在嵌套在函?shù)體內(nèi)
def test6(n):
    def inner1(m):
        new = m + "!!!"
        return new
    def inner2(m):
        new = m + "***"
        return new
    if n > 3:
        return inner2
    else:
        return inner1

result6 = test6(3)
print(result6("tom"))  # tom!!!

# 內(nèi)層函數(shù)對象能夠記憶住父函數(shù)的變量
def test7(n):
    def inner(m):
        return m + n
    return inner

result7 = test7(7)
print(result7(6))  # 13

# 所有的函數(shù)都是對象，但是所有的對象并不一定都是函數(shù)
class A:
    pass

a = A()

def test8():
    pass

from types import FunctionType
print(isinstance(a, A))  # True
print(isinstance(test8, FunctionType))  # True
print(isinstance(a, FunctionType))  # False  所有的對象并不一定都是函數(shù)

# 對象成為函數(shù)需要實(shí)現(xiàn)__call__協(xié)議
class B:
    def __init__(self, n):
        self.n = n
    def __call__(self, m):
        return self.n + m

b = B(9)
print(b(9))  # 18