Python中的返回值是什么

返回值

函数并非总是直接显示输出，相反，它可以处理一些数据，并返回一个或一组值。函数的返回值被称为返回值。

1. 简单的返回值

def get_formatted_name(first_name, last_name):
    full_name = first_name + ' ' + last_name
    return full_name.title()
musician = get_formatted_name('jimi', 'hendrix')
print(musician)

调用返回值的函数时，需要提供一个变量存储返回的值。

2. 让实参变成可选的

def get_formatted_name(first_name, middle_name, last_name):
    full_name = first_name + ' ' + middle_name + ' ' + last_name
    return full_name.title()
musician = get_formatted_name('john', 'lee', 'hooker')
print(musician)

然而并非每个人都有中间名，怎样让中间名变成可选呢？

def get_formatted_name(first_name, last_name, middle_name=' '):
    if middle_name:
        full_name = first_name + ' ' + middle_name + ' ' + last_name
    else:
        full_name = first_name + ' ' + last_name
    return full_name.title()
musician = get_formatted_name('john', 'hooker', 'lee')
print(musician)
musician = get_formatted_name('jimi', 'hendrix')
print(musician)

给形参中间名一个空字符为默认值，将其移动至形参列表的末尾；调用函数时确保实参中间名方最后。

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3. 返回字典

def build_person(first_name, last_name):
    person = {'first': first_name, 'last': last_name}
    return person
musician = build_person('jimi', 'hendrix')
print(musician)

扩展函数，使其接受可选值

def build_person(first_name, last_name, age=' '):
    person = {'first': first_name, 'last': last_name}
    if age:
        person['age'] = age
    return person
musician = build_person('jimi', 'hendrix', age=27)
print(musician)

4. 结合使用函数和while循环

def get_formatted_name(first_name, last_name):
    full_name = first_name + ' ' + last_name
    return full_name.title()
while True:
    print("\nPlease tell me your name:")
    f_name = input("First name: ")
    l_name = input("Last name: ")
    formatted_name = get_formatted_name(f_name, l_name)
    print("\nHello, " + formatted_name + "!")

循环调用定义的函数，say hello everyone!!! 该在什么地方提供推出呢？

def get_formatted_name(first_name, last_name):
    full_name = first_name + ' ' + last_name
    return full_name.title()
while True:
    print("\nPlease 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
    formatted_name = get_formatted_name(f_name, l_name)
    print("\nHello, " + formatted_name + "!")

每次提示用户输入时均可推出。