Python第七课——函数 - 服务器托管|北京服务器租用|机房托管租用|IDC托管租用|机房机柜带宽租用-价格及费用咨询

记忆关键点：

一、定义函数

def greet_user():
    """显示简单的问候语"""
    print("hello!")
greet_user()

def greet_user():
    """显示简单的问候语"""
    print("hello!")
greet_user()

def greet_user(username):
    """显示简单的问候语"""
    print("hello!",username)
greet_user("bob")

注意实参，形参，函数开头用define，冒号的使用

二、传递实参

1、位置实参

要求实参的位置与形参相同

def show_mypets(name,varition):
    print(f"my pet's name is {name},it is a {varition}")
show_mypets("xinxin","my_wife")

实参按对应顺序传递给形参后，在函数体内执行

def show_mypets(name,varition):
    print(f"my pet's name is {name},it is a {varition}")
show_mypets("xinxin","my_wife")
show_mypets("dd",'dog')#多次调用函数

2、关键字实参

无需考虑实参顺序，清楚地指明了函数调用中各个值得用途

def show_mypets(name,varition):
    print(f"my pet's name is {name},it is a {varition}")
show_mypets("xinxin","my_wife")
show_mypets(varition='dog',name="dd")

3、默认值

实参或者形参有默认值了，那么只需要给没有默认值得形参进行实参传递

def show_mypets(name="ggg",varition):
    print(f"my pet's name is {name},it is a {varition}")
show_mypets(varition='dog')#默认为位置实参，发生错误

def show_mypets(name,varition="dog"):
    print(f"my pet's name is {name},it is a {varition}")
show_mypets(name="dsds")

def show_mypets(name,varition="dog"):
    print(f"my pet's name服务器托管网 is {name},it is a {varition}")
show_mypets(name="dsds",varition="cat")#覆盖形参中得原来的赋值

4、等效的函数调用

就是综合位置实参和关键字实参的应用

def show_mypets(name,varition="dog"):
    print(f"my pet's name is {name},it is a {varition}")
show_mypets(name="dsds",varition="cat")#关键字实参
show_mypets("dsds",varition="cat")#位置实参
show_mypets(varition="cat",name="dsds")#关键字实参
show_mypets(name="dsds")#位置实参
show_mypets("dsds")#位置实参
show_mypets("dsds","dog")#位置实参

三、返回值

1、返回简单的值

def full_name(first_name,last_name):
    full_name=f"{first_name}{last_name}"
    return full_name
message=full_name("lai","xiangtiai")
print(message)

2、让实参变成可选的

def full_name(first_name,last_name,middle_name=""):
    #是否有middle——name,有就打印，否则就不打印
    if(middle_name):
        full_name=f"{first_name} {middle_name} {last_name} "
    else:
        full_name=f"{first_name} {last_name}"
    return full_name.title()
message1=full_name("lai","li")
print(message1)
message2=full_name("lai",'hhh',"li")
print(message2)

3、返回字典

函数可以返回任何类型的值，包括列表字典等较为复杂的数据结构

def my_name(first_name,last_name):#返回一个人的信息的字典
    name={"first":first_name,"last":last_name}
    return name
myname=my_name("bob","son")
print(myname)

def my_name_age(first_name,last_name,age):#返回一个人的信息的字典
    name={"first":first_name,"last":last_name}
    if age:
        name["age"]=age#追加到后面
    return name
myname_age=my_name_age("bob","son",27)
print(myname_age)

4、结合使用函数和while循环

使用用户名和姓给用户无限循环地打招呼

def my_name(first_name,last_name):#返回一个人的信息的字典
    full_name=f"{first_name} {last_name}"
    return full_name
while True:
    print("tell me your name?")
    f_name=input("first name:")
    l_name=input("last name:")
    full_name=my_name(f_name,l_name)
    print(f"hello,{full_name}")

用break设置退出条件

def my_name(first_name,last_name):#返回一个人的信息的字典
    full_name=f"{first_name} {last_name}"
    return full_name
while True:
    print("tell me your name?")
    print("enter 'q' at any time to quit")
    f_name=input("first name:")
    if f_name=="q":
        break
    l_name=input("last name:")
    if l_name=='q':
        break
    full_name=my_name(f_name,l_name)
    print(f"hello,{full_name}")

5、传递列表

def greet_users(names):
    for name in names:
        print(f"hello,{name.tit服务器托管网le()}")
names=["zhang",'bob','david']#给列表中的每个人打招呼
greet_users(names)

在函数中修改列表

#首先创建一个列表，其中包含一些要打印的数据
unprinted_designs=['phone case','robot','data']#未打印的设计
completed_models=[]#完成的设计
#模拟打印所有设计
#打印设计后，移到列表completed_models中
while unprinted_designs:
    current_design=unprinted_designs.pop()#每次从列表中最后一个设计打印
    print(f"printing model:{current_design}")
    completed_models.append(current_design)#添加至已完成中
#显示已打印的模型
print("nthe following models have been printed:")
for completed_model in completed_models:
    print(completed_model)

等同于

def print_models(unprinted_designs,completed_models):
    while unprinted_designs:
        current_design = unprinted_designs.pop()  # 每次从列表中最后一个设计打印
        print(f"printing model:{current_design}")
        completed_models.append(current_design)  # 添加至已完成中
def show_completed_models(completed_models):
    """显示打印好的额所有模型"""
    print("nthe following models have been printed:")
    for completed_model in completed_models:
        print(completed_model)
#首先创建一个列表，其中包含一些要打印的数据
unprinted_designs=['phone case','robot','data']#未打印的设计
completed_models=[]#完成的设计
print_models(unprinted_designs,comple

有函数的版本程序更容易拓展和维护，将复杂的任务分解成一系列步骤

禁止函数修改列表

传递列表的副本，让原列表保留

def print_models(unprinted_designs,completed_models):
    while unprinted_designs:
        current_design = unprinted_designs.pop()  # 每次从列表中最后一个设计打印
        print(f"printing model:{current_design}")
        completed_models.append(current_design)  # 添加至已完成中
def show_completed_models(completed_models):
    """显示打印好的额所有模型"""
    print("nthe following models have been printed:")
    for completed_model in completed_models:
        print(completed_model)
#首先创建一个列表，其中包含一些要打印的数据
unprinted_designs=['phone case','robot','data']#未打印的设计
completed_models=[]#完成的设计
print_models(unprinted_designs[:],completed_models)#unprinted_designs[:]复制列表
show_completed_models(completed_models)
print(unprinted_designs)

6、任意传递参数的实参

def make_pizza(*toppings):
    """打印顾客所点的所有配料"""
    print(toppings)
make_pizza("gousi")
make_pizza('sssxs')
make_pizza('ss','sb','sd','sl')
kk=["jo",'dd']
make_pizza(kk)
ll={'ss','xas'}
make_pizza(ll)

def make_pizza(*toppings):
    """打印顾客所点的所有配料"""
    for jj in toppings:
        print(jj)
make_pizza('ss','sb','sd','sl')

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