输入、函数、类、继承

Python

输入

message = input("Tell me something, and I will repeat it back to you:")
print(message)
#input()，接受一个参数，即向用户显示的说明描述
#int()获取数值输入
age = input("How old are you?")  #返回的是一个字符串, 要想使用一个数值，需要用 int()
print(age)
age = int(age)
print(age)

python2.7 输入。raw_input()提示用户输入，输入解读为字符串

函数

1.位置实参

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("dog", "willie")
describe_pet("willie", "dog")

注意：函数调用中实参的顺序要与函数定义中形参的顺序保持一致

2.关键字实参

def describe_pet(animal_type, pet_name):
    """显示宠物的信息"""
    print("\nI hava a "+ animal_type+".")
    print("My "+animal_type+"'s name is "+pet_name.title()+".")
describe_pet(animal_type="dog", pet_name="willie")
describe_pet(pet_name="willie", animal_type="dog")

关键字实参是传递给函数的名称-值对，在实参中将名称和值关联起来。关键字实参无需考虑函数调用中实参的顺序

3. 默认值

def describe_pet(pet_name, animal_type="dog"):
    """显示宠物的信息"""
    print("\nI have a "+animal_type+".")
    print("My "+animal_type+"'s name is "+pet_name.title()+".")
describe_pet(pet_name="willie")
describe_pet("willie")
describe_pet(pet_name="willie", animal_type="cat")
describe_pet(animal_type="cat", pet_name="willie")
describe_pet("willie", "cat")

函数调用中，如果给形参提供了实参时，将使用指定的实参值；否则，将使用形参的默认值

4. 传递任意数量实参

def make_pizza(*toppings):
    """打印顾客点的所有配料"""
    print(toppings)
make_pizza("aa")
make_pizza("aa", "bb", "cc")

形参*toppings 中的星号是让 Python 创建一个名为toppings 的空元组，并将所有收到的值封装到这个元组中。

5. 传递任意数量的关键字实参

def build_profile(first,last,**user_info):
    """创建一个字典，其中包含我们知道的有关用户的一切"""
    profile={}
    profile["first_name"] = first
    profile["last_name"] = last
    for key, value in user_info.items():
        profile[key] = value
user_profile = build_profile("albert", "einstein", location="princeton", field="physics")
print(user_profile)

形参 **user_info 中的两个星号让 Python 创建一个名为 user_info的空字典，并将收到的所有名称-值对都封装到这个字典中。

模块

1. 导入整个模块

#pizza.py
def make_pizza(size, *toppings):
    """概述要制作的比萨"""
    print("\nMaking a " + str(size)+"-inch pizza with the following toppings:")
    for topping in toppings:
        print("- "+topping)
#pizza.py 同目录下创建making_pizza.py
import pizza
pizza.make_pizza(16, "aa")
pizza.make_pizza(12, "aa", "cc", "dd")

通用语法:module_name.function_name()

2. 导入特定的函数

from pizza import make_pizza
make_pizza(16, "aa")
make_pizza(12, "aa", "cc", "dd")

3. as 给函数指定别名

from pizza import make_pizza as mp
mp(16, "aa")
mp(12, "aa", "cc", "dd")

如果要导入的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。

4. as 给模块指定别名

import pizza as p
p.make_pizza(16, "aa")
p.make_pizza(12, "aa", "cc", "dd")

5. 导入模块中所有函数

from pizza import *

类

1. 创建类

class Dog():
    """一次模拟小狗的简单尝试"""
    def __init__(self, name, age):
        """初始化属性 name 和 age"""
        self.name = name
        self.age = age
    def sit(self):
        """模拟小狗被命令时蹲下"""
        print(self.name.title() + " is now sitting.")
    def roll_over(self):
        """模拟小狗被命令时打滚"""
        print(self.name.title() + " rolled over!")
    def update_dog(self, name):
        """修改属性name值"""
        self.name = name

补充说明:Python2.7创建类时，需要在括号内包含单词 object 。类似如: class Dog(object)

2. 创建实例

my_dog = Dog("willie", 6)

• 访问属性
  my_dog.name, my_dog.age
• 调用方法
  my_dog.sit(), my_dog.roll_over()
• 修改属性的值
  
  • 直接改
    my_dog.name = "Mary"
  • 通过方法改
    my_dog.update_dog("mary")

3. 继承

class Car():
    """一次模拟汽车的简单尝试"""
    def __init__(self, make, model, year):
        self.make = make
        self.model = model
        self.year = year
        self.odometer_reading = 0
    def get_descriptive_name(self):
        long_name = str(self.year)+" "+self.make+" "+self.model
        return long_name.title()
    def read_odometer(self, mileage):
        print("This car has " + str(self.odometer_reading) + " miles on it.")
    def update_odometer(self, mileage):
        if mileage >= self.odometer_reading:
            self.odometer_reading = mileage
        else:
            print("You can't roll back on odometer!")
    def increment_odometer(self, miles):
        self.odometer_reading += miles
    def run(self):
        print("汽车在跑")
class Battery():
    """将电瓶这部分独立出来作为一个类"""
    def __init__(self, battery_size=70):
        self.battery_size = battery_size
    def describe_battery(self):
        print("This car has a " + str(self.battery_size) + "-kwh battery.")
class ElectricCar(Car):
    """电动汽车的独特之处"""
    def __init__(self, make, model, year):
        """初始化父类的属性,再初始化电动汽车特有的属性"""
        super().__init__(make, model, year)
        self.battery_size = 70      #子类添加新属性self.battery_size
        self.battery = Battery()    #将实例Battery()用作ElectricCar的属性self.battery
    def describe_battery(self):
        """打印一条描述电瓶容量的消息, 子类添加新方法describe_battery"""
        print("This car has a " + str(self.battery_size) + "-kwh battery.")
    def run(self):
        """重写父类方法run"""
        print("电动汽车在跑")
my_tesla = ElectricCar("tesla", "models", 2016)
print(my_tesla.get_descriptive_name())
my_tesla.describe_battery()

创建子类时，父类与子类必须同处一个文件中，并且父类在子类前面。定义子类时，必须在括号里指明父类的名称。super()，将父类和子类关联起来。

注意: Python2.7继承语法如下

class Car(object):
    def __init__(self, make, model, year):
        --snip--
class ElectricCar(Car):
    def __init__(self, make, model, year):
        super(ElectricCar, self).__init__(make, model, year)
        --snip--

super()需要两个实参：子类名和对象 self。父类在括号里指定object

三个引号表示文档注释