11_函数

创建和调用函数

# I Love You
# I Love You
# I Love You
def myfunc():
    for i in range(3):
        print("I Love You")
myfunc()

函数的参数

# I Love python
# I Love python
# I Love python
# I Love python
# I Love python
def myfunc(name,time):
    for i in range(time):
        print(f"I Love {name}")
myfunc("python",5)

函数返回

def div(x, y):
    z = x / y
    return z
div(4, 2)
-----------------------------
def div(x, y):
    if y == 0:
        return "除数不能为0！"
    else:
        return x / y
print(div(4, 2))

函数参数

# 位置参数
def myfunc(s, vt, o):
    return "".join((o, vt, s))
print(myfunc("我", "打了", "你"))
# 关键字参数
print(myfunc(o="我", vt="打了", s="你"))
# 位置参数必须在关键字参数之前
print(myfunc("我", vt="打了", s="你"))
# 默认参数
def myfunc(s, vt, o = "她"):
    return "".join((o, vt, s))
print(myfunc("我", "打了"))

----------------------------------------
# 收集参数 print()
def myfunc(*args):
    # 有2个参数。
    # 第2个参数是：我打算
    print("有{}个参数。".format(len(args)))
    print("第2个参数是：{}".format(args[1]))
myfunc("小甲鱼", "我打算")

# 利用元组进行打包
# 返回值是一个元组(1, 2, 3)
def myfunc():
    return 1, 2, 3
print(myfunc())
# 元组解包
x, y, z = myfunc()
print(x)
print(y)
print(z)
# (1, 2, 3) 4 5
def myfunc(*args, a, b):
    print(args, a, b)
myfunc(1, 2, 3, a=4, b=5)

# 收集参数打包成字典
def myfunc(**kwargs):
    print(kwargs)
# {'a': 1, 'b': 2, 'c': 3}
myfunc(a=1, b=2, c=3)

def myfunc(a, *b, **c):
    print(a, b, c)
# 1 (2, 3, 4) {'x': 5, 'y': 6}
myfunc(1, 2, 3, 4, x=5, y=6)

# 解包参数
args = (1, 2, 3, 4)
def myfunc(a, b, c, d):
    print(a, b, c, d)
#  1 2 3 4
myfunc(*args)
kwargs = {'a': 1, 'b': 2, 'c': 3, 'd': 4}
#  1 2 3 4
myfunc(**kwargs)
-----------------------------------------------

作用域

# 全局变量
x = 520
def myfunc():
    # 局部变量
    x = 1314
    print(x)
# 1314
myfunc()
# 520
print(x)

# 在函数里面修改全局变量,global修改的是函数体外的全局变量
x = 1314
def myfunc():
    global x
    x = 520
    print(x)
# 520
myfunc()
# 520,此时的全局变量已经在函数里面修改了
print(x)

# 嵌套函数,nonlocal 修改的是上一层嵌套的函数变量，若有多层嵌套也只修改上一层，上一层要是没有局部变量，直接报错
def funA():
    x = 520
    def funB():
        x = 1314

        print("In funB, x =", x)
    # In funB, x = 1314
    funB()
    print("In funA, x =", x)
# In funA, x = 520
funA()
def funA():
    x = 520
    def funB():
        nonlocal x
        x = 1314
        print("In funB, x =", x)
    # In funB, x = 1314
    funB()
    print("In funA, x =", x)
# In funA, x = 1314,此时上一层嵌套的函数变量被函数体修改
funA()
--------------------------------------------------------

闭包

def power(exp):
    def exp_of(base):
        # 幂运算
        return base ** exp
    return exp_of
square = power(2)
cube = power(3)
# 4
print(square(2))
# 25
print(square(5))
# 8
print(cube(2))
# 125
print(cube(5))

def outer():
    x = 0
    y = 0
    def inner(x1, y1):
            nonlocal x, y
            x += x1
            y += y1
            print(f"现在，x = {x}, y = {y}")
    return inner
move = outer()
# 现在，x = 1, y = 2
move(1, 2)
# 现在，x = -1, y = 4
move(-2, 2)

装饰器

def myfunc():
    print("正在调用myfunc....")


def report(func):
    print("开始调用函数...")
    func()
    print("调用函数完毕！")
# 开始调用函数...
# 正在调用myfunc....
# 调用函数完毕！
report(myfunc)
-----------------------------------------
# 装饰器
@time_master
def myfunc():
    time.sleep(2)
    print("hello,love")

时间管理大师函数

import time
def time_master(func):
    print("开始运行程序>>>")
    start = time.time()
    func()
    stop = time.time()
    print("结束程序运行>>>")
    print(f"一共耗时:{(stop-start):.2f}秒")
def myfunc():
    time.sleep(2)
    print("hello,love")

time_master(myfunc)

lambda表达式

# 常规函数实现求平方
def squareX(x):
    return x * x
print(squareX(3))
# lambda表达式实现
squareY = lambda y : y * y
print(squareY(3))

生成器

def fib():
    back1, back2 = 0, 1
    while True:
        yield back1
        back1, back2 = back2, back1 + back2
f = fib()
# 0
# 1
# 1
# 2
# 3
print(next(f))
print(next(f))
print(next(f))
print(next(f))
print(next(f))
---------------------------------------------
def funA():
    print('我是A函数')

def funB():
    funA()
def funC(i):
    if i > 0:
        print("我是C函数")
        i -= 1
        funC(i)
funC(10)

函数文档

# help(print())
def exchange(dollar, rate = 6.32):
    """
    功能：汇率换算，美元-> 人民币
    参数
    - dollar: 美元数量
    - rate: 汇率，默认值是 6.32（2022-7-5）
    返回值：
    - 人民币的数量
    """
    return dollar * rate
print(exchange(20))
(help(exchange))

# 类型注释
def times(s:str, n:int) -> str:
    return s * n
# lovelovelovelovelove
print(times("love", 5))

def times(s:list, n:int = 3) -> list:
    return s * n
# [1, 2, 3, 1, 2, 3, 1, 2, 3]
print(times([1, 2, 3]))

def times(s:dict[str,int], n:int = 3) -> list:
    return list(s.keys()) * n
# ['A', 'B', 'C', 'A', 'B', 'C', 'A', 'B', 'C']
print(times({'A':1,'B':2,'C':3}))

# 内省
# {'s': dict[str, int], 'n': <class 'int'>, 'return': <class 'list'>}
print(times.__annotations__)
#     功能：汇率换算，美元-> 人民币
#     参数
#     - dollar: 美元数量
#     - rate: 汇率，默认值是 6.32（2022-7-5）
#     返回值：
#     - 人民币的数量
print(exchange.__doc__)