Python学习之函数

    函数这章的学习效率比较低。

#定义函数def greet_user(username):"""显示简单的问候语"""print("Hello, "  + username .title()+ "!")greet_user('jesse')"""username是个形参，jesse是实参，它被存储在形参username中"""#位置实参传递def describe_pet(animal_type,pet_name):"""显示宠物信息"""print("\nI have a " + animal_type + ".")print("My " + animal_type + "'s name is " + pet_name.title() + ".")describe_pet('hamster','harry')#关键字实参"""关键字实参的顺序无关紧要，使用时的形参名一定要准确"""def describe_pet(animal_type,pet_name):"""显示宠物信息"""print("\nI have a " + animal_type + ".")print("My " + animal_type + "'s name is " + pet_name.title() + ".")describe_pet(animal_type = 'hamster',pet_name = 'harry')#默认值"""使用默认值时在形参列表中必须先列出没有默认值的形参，        在列出有默认值的形参以便能够正确解读位置实参"""def describe_pet(pet_name,animal_type = 'dog'):"""显示宠物信息"""print("\nI have a " + animal_type + ".")print("My " + animal_type + "'s name is " + pet_name.title() + ".")describe_pet(pet_name = 'willie')#等效实参def describe_pet(pet_name,animal_type = 'dog'):print("\nMy " + animal_type + "'s name is " + pet_name.title() + "!")describe_pet('willie')describe_pet(pet_name = 'willie')describe_pet('harry','hamster')describe_pet(pet_name = 'harry',animal_type = 'hamster')describe_pet(animal_type = 'hamster',pet_name = 'harry')#返回值和实参的可选性def get_formatted_name(first_name,last_name,middle_name = ''):"""返回完整的姓名"""if middle_name:full_name = first_name + ' ' + middle_name + ' ' + last_nameelse:full_name = first_name + ' ' +last_namereturn full_name.title()musician = get_formatted_name('jimi','hendrix')print("\n" + musician)musician = get_formatted_name('jahn','hooker','lee')print("\n" + musician)#返回字典def build_person(first_name,last_name,age = ''):person = {'first':first_name,'last':last_name}if age:person['age'] = agereturn personmusician = build_person('jimi','hendrix',age = 27)print(musician)#传递列表def greet_users(names):for name in names:msg = "Hello, " + name.title() + "!"print(msg)usernames = ['hannah','ty','margot']greet_users(usernames)#传递任意数量的实参结合使用位置实参def make_pizza(size,*toppings):"""*toppings是创建一个名为toppings的空元组，所接受到的值都封装到元组中"""print("\nMaking a " + str(size) + "-inch pizza with the following toppings:")for topping in toppings:print("- " + topping)make_pizza(16,'pepperoni')make_pizza(12,'mushrooms','green peppers','extra cheese')"""一般是位置实参和关键字实参先匹配，因此将接受任意数量实参的形参放在最后"""#使用任意数量的关键字参数"""**user_info表示创建一个名为user_info的空字典并将所有收到的名称值都封装到这个字典中"""def build_profile(first,last,**user_info):profile = {}profile['firstname'] = firstprofile['lastname'] = lastfor key,value in user_info.items():profile[key] = valuereturn profileuser_profile = build_profile('albert','einstein',location = 'princeton',field = 'physics')print(user_profile)