Python编程-第八章-函数
一个简单的函数定义
def greet_user():
""" Show simple greeting """
print("Hello!")
greet_user()
# 传入参数
def greet_user(username):
""" Show simple greeting """
print(f"Hello, {username.title()}!")
greet_user('Jesse')
8.1.2 实参和形参
在函数greet_user() 的定义中，变量username 是一个形参 （parameter）
在代码greet_user('jesse') 中，值'jesse' 是一个实参 （argument）
练习题
练习8-1：消息 编写一个名为display_message() 的函数，它打印一个句子，指出你在本章学的是什么。调用这个函数，确认显示的消息正确无误。
def display_message():
print(f"This chapter is learning about functions.")
display_message()
def favorite_book(title):
print(f"My favorite books are:{title.title()}")
favorite_book('utopia')
传递实参
# 位置实参
def describe_pet(animal_type,pet_name):
"""Show pet information"""
print(f"\nI have a {animal_type}.")
print(f"My {animal_type}'s name is {pet_name.title()}.")
describe_pet('hamster','harry')
# 关键字实参
def describe_pet(animal_type,pet_name):
"""Show pet information"""
print(f"\nI have a {animal_type}.")
print(f"My {animal_type}'s name is {pet_name.title()}.")
describe_pet(animal_type='hamster',pet_name='harry')
参数默认值
def describe_pet(animal_type='dog',pet_name='alice'):
"""Show pet information"""
print(f"\nI have a {animal_type}.")
print(f"My {animal_type}'s name is {pet_name.title()}.")
describe_pet(pet_name='whillie')
练习题
def make_shirt(size,symbol):
print(f"Make size of {size},print {symbol} printedWords")
make_shirt(size='XXL',symbol='kingbase')
# 添加默认值
def make_shirt(size='XXL',symbol='I love Python'):
print(f"Make size of {size},print {symbol} printedWords")
make_shirt(size='XXL',symbol='kingbase')
make_shirt()
返回值
def get_formatted_name(first_name,last_name):
"""Returns the neat name. """
full_name = f"{first_name} {last_name}"
return full_name.title()
musician = get_formatted_name('jimi','hendrix')
print(musician)
可选参数
def get_formatted_name(first_name,last_name,middle_name=''):
"""Returns the neat name. """
if middle_name:
full_name = f"{first_name} {middle_name} {last_name}"
else:
full_name = f"{first_name} {last_name}"
return full_name.title()
musician = get_formatted_name('jimi','hendrix')
print(musician)
musician = get_formatted_name('jimi','hoooker','hendrix')
print(musician)
返回字典
def get_formatted_name(first_name,last_name,middle_name=''):
"""Returns the neat name. """
if middle_name:
person={'first': first_name,'midll_name': middle_name,'last': last_name}
else:
person = {'first': first_name, 'last': last_name}
return person
musician = get_formatted_name('jimi','hendrix')
print(musician)
musician = get_formatted_name('jimi','hoooker','hendrix')
print(musician)
可选参数配置
def build_person(first_name,last_name,age=None):
"""Returns a dictionary containing information about a person. """
person = {'first': first_name,'last': last_name}
"""If age has an incoming parameter, it will be assigned. """
if age:
person['age']=age
return person
musician = build_person('jimi','hendrix',age=27)
print(musician)
和while 循环结合使用函数
def get_formatted_name(first_name,last_name):
"""Returns the neat name. """
full_name = f"{first_name} {last_name}"
return full_name.title()
# This is an infinite loop.
while True:
print("\nPlease tell me your name:")
print("\nenter '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
formattted_name =get_formatted_name(f_name,l_name)
print(f"\nHello, {formattted_name}!")
练习题
def city_country(city,country):
message=f"{city},{country}"
return message
values=city_country('newyork','America')
print(f"\"{values}\"")
练习8-7：专辑 编写一个名为make_album() 的函数，它创建一个描述音乐专辑的字典。这个函数应接受歌手的名字和专辑名，并返回一个包含这两项信息的字典。使用这个函数创建三个表示不同专辑的字典，并打印每个返回的值，以核实字典正确地存储了专辑的信息。
给函数make_album() 添加一个默认值为None 的可选形参，以便存储专辑包含的歌曲数。如果调用这个函数时指定了歌曲数，就将该值添加到表示专辑的字典中。调用这个函数，并至少在一次调用中指定专辑包含的歌曲数
def make_album(name,album_name,numberOfAlbums=None):
if numberOfAlbums:
album={'name': name ,'ablum_name': album_name,'number': numberOfAlbums}
else:
album={'name': name ,'ablum_name': album_name}
return album
current_album=make_album('linkpark','alice')
print(f"{current_album}")
current_album=make_album('linkpark','alice')
print(f"{current_album}")
current_album=make_album('linkpark','alice')
print(f"{current_album}")
current_album=make_album('linkpark','alice','23')
print(f"{current_album}")
def make_album(name,album_name,numberOfAlbums=None):
if numberOfAlbums:
album={'name': name ,'ablum_name': album_name,'number': numberOfAlbums}
else:
album={'name': name ,'ablum_name': album_name}
return album
while True:
print("\nPlease enter an album infomation. ")
print("\nPlease enter 'q' to exit the program. ")
p_name = input("name:")
if p_name == 'q':
break
a_name = input("ablum name:")
if a_name == 'q':
break
n_number = input("ablum number:")
if n_number == 'q':
break
ablum = make_album(p_name,a_name,n_number)
print(f"\nHello,{ablum}!")
传递列表
def greet_users(names):
"""Send a simple greeting to each user on the list. """
for name in names:
msg = f"Hello,{name.title()}!"
print(msg)
usernames=['hannah','ty','margot']
greet_users(usernames)
在函数中修改列表
def print_models(unprinted_designs,completed_models):
# Simulate printing each design until there are no unprinted designs.
# After printing each design, move it to the list completed models.
while unprinted_designs:
current_design = unprinted_designs.pop()
print(f"Printing model: {current_design}")
completed_models.append(current_design)
# Displays all printed models.
def show_completed_modes(completed_models):
print("\nThe following modes have been prited:")
for completed_model in completed_models:
print(completed_model)
unprinted_designs=['phone case','robot pendant','dodecahedron']
completed_models = []
print_models(unprinted_designs,completed_models)
show_completed_modes(completed_models)
禁止修改列表
切片表示法[:] 创建列表的副本。在printing_models.py中，如果不想清空未打印的设计列表，可像下面这样调用print_models()
# 调用函数时，使用`unprinted_designs[:]`
unprinted_designs=['phone case','robot pendant','dodecahedron']
completed_models = []
print_models(unprinted_designs[:],completed_models)
show_completed_modes(completed_models)
练习题
练习8-9：消息 创建一个列表，其中包含一系列简短的文本消息。将该列表传递给一个名为show_messages() 的函数，这个函数会打印列表中的每条文本消息
def show_messages(msg):
for msg_values in msg:
print(f"{msg_values}")
msg =['test','waring','list','history']
show_messages(msg)
def send_messages(unsend_msg,send_msg):
while unsend_msg:
current_msg = unsend_msg.pop()
print(f"send model:{current_msg}")
send_msg.append(current_msg)
def show_messages(msg):
for msg_values in msg:
print(f"{msg_values}")
msg =['test','waring','list','history']
unsend_msg=['alice','fwaring','list','history']
send_msg=[]
send_messages(unsend_msg,send_msg)
show_messages(send_msg)
def send_messages(unsend_msg,send_msg):
while unsend_msg:
current_msg = unsend_msg.pop()
print(f"send model:{current_msg}")
send_msg.append(current_msg)
def show_messages(msg):
for msg_values in msg:
print(f"{msg_values}")
msg =['test','waring','list','history']
unsend_msg=['alice','fwaring','list','history']
send_msg=[]
send_messages(unsend_msg[:],send_msg)
show_messages(send_msg)
show_messages(unsend_msg)
传递任意数量的实参
形参名*toppings 中的星号让Python创建一个名为toppings 的空元组
def make_pizza(*toppings):
"""Print all the ingredients ordered by the customer"""
print(f"\nMaking a pizza with the following toppings:")
for topping in toppings:
print(f"- {topping}")
make_pizza('pepperroni')
make_pizza('mushrooms','gree pepperes','extra cheese')
固定数量的实参和任意数量的实参
def make_pizza(size,*toppings):
"""Print all the ingredients ordered by the customer"""
print(f"\nMaking a{size} pizza with the following toppings:")
for topping in toppings:
print(f"- {topping}")
make_pizza(16,'pepperroni')
make_pizza(12,'mushrooms','gree pepperes','extra cheese')
使用任意数量的关键词实参
使用任意数量的关键字实参
形参**user_info 中的两个星号让Python创建一个名为user_info的空字典，
def build_profile(first,last,**user_info):
"""Create a dictionary with all the user's information. """
user_info['first_name'] = first
user_info['last_name'] =last
return user_info
user_profile=build_profile('albert','einstein',locaion='princeton',field='physics')
print(user_profile)
练习题
def make_sandwich(*toppings):
for topping in toppings:
print(f"- {topping}")
make_sandwich('mushrooms')
make_sandwich('mushrooms','green peppers','extra cheess')
练习8-13：用户简介 复制前面的程序user_profile.py，在其中调用build_profile() 来创建有关你的简介。调用这个函数时，指定你的名和姓，以及三个描述你的键值对
def build_profile(first,last,**user_info):
"""Create a dictionary with all the user's information. """
user_info['first_name'] = first
user_info['last_name'] =last
return user_info
user_profile=build_profile('chen','cheng',locaion='china',field='physics',province='chongqing')
print(user_profile)
def make_cars(product,modle,**cars_info):
"""Create a dictionary with all the user's information. """
cars_info['product'] = product
cars_info['modle'] =modle
return cars_info
car=make_cars('subaru','outback',color='blue',tow_package='True')
print(car)
将函数存储在模块中
你还可以更进一步，将函数存储在称为模块 的独立文件中，再将模块导入 到主程序中。import 语句允许在当前运行的程序文件中使用模块中的代码。
导入整个模块
def make_pizza(size,*toppings):
"""Outline the pizza to be made. """
print((f"\nMaking a {size}-inch pizza with the following topping:"))
for topping in toppings:
print(f"-{topping}")
接下来，在pizza.py所在的目录中创建一个名为making_pizzas.py的文件。这个文件导入刚创建的模块，再调用make_pizza() 两次
import pizza
pizza.make_pizza(16,'pepperoni')
pizza.make_pizza(16,'pepperoni','mushrooms','green peppers','extra cheese')
Note
import 操作是将对应的模块里面的内容加入到当前代码里 。
导入特定的函数
from pizza import make_pizza
make_pizza(16,'pepperoni')
make_pizza(16,'pepperoni','mushrooms','green peppers','extra cheese')
Warning
如果只导入函数，可以使用上面的语法。
如果只导入函数，则可以省略模块名称。
使用AS 给函数别名
如果要导入函数的名称可能与程序中现有的名称冲突，或者函数的名称太长，可指定简短而独一无二的别名 ：函数的另一个名称，类似于外号。要给函数取这种特殊外号，需要在导入它时指定
from pizza import make_pizza as mp
mp(16,'pepperoni')
mp(16,'pepperoni','mushrooms','green peppers','extra cheese')
使用AS 给模块指定别名
import pizza as p
p.make_pizza(16,'pepperoni')
p.make_pizza(16,'pepperoni','mushrooms','green peppers','extra cheese')
导入模块中的所有函数
from pizza import *
# import pizza as p
make_pizza(16,'pepperoni')
make_pizza(16,'pepperoni','mushrooms','green peppers','extra cheese')
Warning
导入模块中的所有函数，这样就可以不用写模块名称。
但是要注意，为了代码更加容易阅读，最好只导入需要的函数名称。
函数编写指南
1、应给函数指定描述性名称，且只在其中使用小写字母和下划线。
2、每个函数都应包含简要地阐述其功能的注释。该注释应紧跟在函数定义后面，并采用文档字符串格式。
3、给形参指定默认值时，等号两边不要有空格：
def function_name(parameter_0, parameter_1='default value')
def function_name(
parameter_0, parameter_1, parameter_2,
parameter_3, parameter_4, parameter_5):
练习题
练习8-16：导入 选择一个你编写的且只包含一个函数的程序，将该函数放在另一个文件中。在主程序文件中，使用下述各种方法导入这个函数，再调用它：
from printing_function import print_models
from printing_function import show_completed_modes
unprinted_designs=['phone case','robot pendant','dodecahedron']
completed_models = []
print_models(unprinted_designs,completed_models)
show_completed_modes(completed_models)