【免费分享编程笔记】Python学习笔记（二）-阿里云开发者社区

【免费分享编程笔记】Python学习笔记（一）+https://developer.aliyun.com/article/1621227

五、if语句

5.1引入例子

cars=['audi','bmw','subaru','toyota']
for car in cars:
    if car=='bmw':
        print(car.upper())
    else:
        print(car.title())

5.2条件测试

每条if语句的核心就是一个值 true或 false。

5.2.1检查多个条件

使用 and检查多个条件，相当于“&&”

age_0=22
age_1=18
print(age_0>=21 and age_1>21)

使用 or检查多个条件，相当于“||”

age_0=22
age_1=18
print(age_0>=21 or age_1>21)

5.2.2检查特定值是否包含在列表中

关键字 in

requested_toppings=['mushrooms','onions','pineapple']
print('mushrooms' in requested_toppings)

在if语句中，缩进的作用与for循环中相同，如果测试通过了，将执行if语句后面所有缩进的代码，否则将忽略他们。

5.3.2if-else语句

age=17
if age>=18:
    print("you are oil enough to vote")
    print("you are oil enough to vote123456")
else:
    print("sorry you can   ")
    print("sorry you can  please register ")

5.3.3if-elif-else

age=12
if age<4:
    print("your admission cost is 0$")
elif age<18:
    print("your admission cost is 5$")
else:
    print("your admission cost is 0$")

5.3.4使用多个elif代码块

age=12
if age<14:
    price=0
elif age<18:
    price=5
elif age<65:
    price=10
else:
    price=5
print("your admission cost is $"+str(price)+".")

六、字典

字典就是能够存储互不相联的信息

alien_0={'color':'green','points':5}
print(alien_0['color'])
print(alien_0['points'])

6.2使用字典

字典是一系列的 键------值对 组成的。我们可以通过键访问值，也可以通过值访问键。

6.2.1访问字典中的值

alien_0={'color':'green','points':5}
new_points=alien_0['points']
print("you just earned "+str(new_points)+"points!")

6.2.2添加键值对

字典是一种动态结构，可以随时添加键值对。

alien_0={'color':'green','points':5}
print(alien_0)
alien_0['x_position']=0
alien_0['y_position']=25
print(alien_0)

6.2.3创建空字典

alien_0={}
alien_0['color']='green'
alien_0['points']=5
print(alien_0)

6.2.4修改字典中的值

alien_0={'color':'green'}
print("The alien is"+alien_0['color']+".")
alien_0['color']='yellow'
print("The alien is now"+alien_0['color']+".")

alien_0={'x_position':0,'y_position':25,'speed':'medium'}
print("Original x-position:"+str(alien_0['x_position']))
#向右移动外星人
#据外星人当前速度决定其移动多远
if alien_0['speed']=='slow':
    x_increment=1
elif alien_0['speed']=='medium':
    x_increment=2
else:
    #这个外星人的移动速度一定很快
    x_increment=3
#新位置等于老位置加上增量
alien_0['x_position']=alien_0['x_position']+x_increment
print("New x-position:"+str(alien_0['x_position']))

6.2.5删除键值对

alien_0={'color':'green','points':5}
print(alien_0)
del alien_0['points']
print(alien_0)

6.2.6由类似对象组成的字典

favorite_languagres={
    'jen':'python',
    'sarah':'C',
    'edward':'ruby',
    'phil':'python',
}
print("Saras facorite language is"+favorite_languagres['sarah'].title()+".")

6.3遍历字典

6.3.1遍历所有的键值对

items()方法可以返回字典里的键和值得元素

user_0={
    'username':'efermi',
    'first':'enrico',
    'last':'fermi',
}
for key,value in user_0.items():
    print("\nkey:"+key)
    print("value:"+value)

6.3.2遍历字典中的所有键

在不需要使用字典中的值时，方法 key（）很有用。遍历所有键值。

favorite_languages={
    'jen':'python',
    'sarah':'c',
    'edward':'ruby',
    'phil':'python',
}
for name in favorite_languages.keys():
    print(name.title())

favorite_languages={
    'jen':'python',
    'sarah':'c',
    'edward':'ruby',
    'phil':'python',
}
friends=['phil','sarah']
for name in favorite_languages.keys():
    print(name.title())
    if name in friends:
        print("Hi"+name.title()+",I see your favorite languages is"+favorite_languages[name].title()+"!")

6.3.3按顺序遍历字典中的所有键

favoirte_languages={
    'jen':'python',
    'sarah':'c',
    'edward':'ruby',
    'phil':'python',
}
for name in sorted(favoirte_languages.keys()):
    print(name.title()+",thank you for taking the poll")

6.3.4遍历字典中的所有值

favoirte_languages={
    'jen':'python',
    'sarah':'c',
    'edward':'ruby',
    'phil':'python',
}
print("The following languages have been menthioned:")
for language in favoirte_languages.values():
    print(language.title())

6.4嵌套

将字典存储在列表中叫做嵌套

6.4.1字典列表

#字典
alien_0={
    'color':'green',
    'points':5,
}
alien_1={
    'color':'red',
    'points':15,
}
alien_2={
    'color':'yellow',
    'points':25,
}
aliens=[alien_0,alien_1,alien_2]#列表
for alien in aliens:
    print(alien)

6.4.2在字典中存储列表

pizza={
    'crust':'thick',
    'toppings':['mushrooms','extra cheese'],
}
print("you ordered a "+pizza['crust']+"-crust pizza"+"with the following toppings:")
for topping in pizza['toppings']:
    print("\t"+topping)

6.4.3在字典中存储字典

users={
    'aeinstein':{
        'first':'albert',
        'last':'einstein',
        'location':'princetion',
    },
    'mucire':{
        'first':'marie',
        'last':'curie',
        'location':'princetion',
    },
}
for username,user_info in users.items():
    print("\nusername:"+username)
    full_name=user_info['first']+" "+user_info['last']
    location=user_info['location']
    print("\tFull name:"+full_name.title())
    print("\tLocation:"+location.title())

七、用户输入和while循环

7.1函数input

这是一个输入函数

message=input("tell me something and I will repeat it back to you:")
print(message)

7.1.1编写清晰的程序

name=input("please enter your name:")
print("Hello"+name+"!")

7.1.2使用int（）来获取数值输入

int()可以将字符串转换成数字

age=input("How old are you?")
age=int(age)
if age>18:
    print("\n you are tall enough to ride")
else:
    print("\n you .....")

7.1.3求模运算符

number=input("Enter a number ,and I will tell you if it is even or odd")
number=int(number)
if number%2==0:
    print("\nThe number"+str(number)+"is even")
else:
    print("\nThe number "+str(number)+"is odd")

7.2while循环简介

7.2.1使用while循环

current_number=1
while current_number<=5:
    print(current_number)
    current_number+=1;

7.2.2让用户选择何时退出

可以使用while循环让程序在用户愿意时不断运行。我们在其中定义一个退出值，只要用户输入的不是这个值，程序接着运行。

prompt="\n Tell me something and i will repeat it back to you:"
prompt+="\n Enter 'quit' to end the program"
message=""
while message !='quit':
    message=input(prompt)
    print(message)

7.2.3使用标志

使用标志有点类似与旗帜变量。赋予它一个状态，当状态发生改变时，循环结束。

prompt="\n Tell me something and i will repeat it back to you:"
prompt+="\n Enter 'quit' to end the program"
active=True
while active:
    message=input(prompt)
    if message=='quit':
        active=False
    else:
        print(message)

7.2.4适应break退出循环

要退出while循环，不在执行接下来的代码，直接使用 break

prompt="\n Tell me something and i will repeat it back to you:"
prompt+="\n Enter 'quit' to end the program"
while True:
    city=input(prompt)
    if city=='quit':
        break
    else:
        print("I love to go to "+city.title()+"!")

7.3使用while循环来处理列表和字典

7.3.1在列表之间移动元素

#首先创建一个带验证的用户列表
#和一个用于存储已经验证的用户列表
unconfirmed_users=['alice','brain','candace']
confirmed_users=[]
#验证每个用户，直到没有未验证的用户为止
#将每个经过验证的列表都移动到已经验证后的用户列表中
while unconfirmed_users:
    current_user=unconfirmed_users.pop()
    print("Verfing user:"+current_user.title())
    confirmed_users.append(current_user)
    #显示所有已经验证的用户
print("\nThe following users have beeen confimede:")
for confirmed_user in confirmed_users:
    print(confirmed_user.title())

7.3.2删除包含特定值的所有列表

pets=['dog','cat','dog','goldfish','cat','rabbit','cat']
print(pets)
while 'cat' in pets:
    pets.remove('cat')
print(pets)

八、函数

8.1定义函数

使用关键字 def

def greeter_user():
    print("Hello!")
greeter_user()

8.1.1向函数传递信息

函数内可以包含参数，我们在调用函数的时候可以自定义参数值进行传递

def greeter_user(username):
    print("Hello!"+username.title())
greeter_user('jesse')

8.1.2实参和形参

调用函数传递的参数叫实参，因为它发挥了实际作用。
定义函数的参数叫形参，只是一个摆设而已，可有可无，所以叫形参。

def describe_pet(animal_type,pet_name):
    print("\nI have a "+animal_type+".")
    print("my"+animal_type+"name is"+pet_name.title()+".")
describe_pet('hasmter','harry')

8.2返回值

函数并非是直接输出显示，相反，他可以处理一些数据，返回一个或一组值。函数返回的值被称为返回值、

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

8.2.1让实参变成可选

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()
muscian=get_formatted_name('jimi','hendrix')
print(muscian)
muscians=get_formatted_name('jimi','hooker','lee')
print(muscians)

8.3传递列表

函数实参为列表

def greet_users(names):
    for name in names:
        msg="Hello,"+name.title()+"!"
        print(msg)
usernames=['hanana','ty','margot']
greet_users(usernames)

8.3.1在函数中修改列表

#首先创建一个列表，其中一些包含要打印的设计
unprinted_designs=['iphone case','robot pendant','dodecahedron']
completed_models=[]
#模拟打印这个设计，知道未打印的设计为止
#打印每个设计后，都将其移动到completed_models中
while unprinted_designs:
    current_design=unprinted_designs.pop()
    #模拟根据设计制作3D打印的过程：
    print("Printing model:"+current_design)
    completed_models.append(current_design)
#显示并打印好所有的模型：
print("\nThe following models have been printed:")
for completed_model in completed_models:
    print(completed_model)

8.5传递任意数量的实参

形如 *topping的参数我们称为一个元组。
元组可以接受多个实参，这样做的好处就是形参不用写多个来匹配了！

def make_pizza(*toppinhs):
    print(toppinhs)
make_pizza('peperoni')
make_pizza('mushrooms','green peppers','extra cheese')
def make_pizza(*toppings):
    print("\n making  a pizza with following toppings:")
    for topping in toppings:
        print("-"+topping)
make_pizza('peperoni')
make_pizza('mushrooms','green peppers','extra cheese')

8.6将函数存储在模块中

8.6.1导入整个模块

将函数存储在被称为模块的独立文件中，再将模块导入到主程序中。
关键字 import

pizza.py:

def make_pizza(size,*toppings):
    print("\n making a"+str(size)+
          "-inch pizza with the following toppings:")
    for topping in toppings:
        print("-"+topping)

making_pizzas.py:

import pizza
pizza.make_pizza(16,'pepperoni')
pizza.make_pizza(12,'mushroom','pepperoni','green peppers','extra cheese')

8.6.2导入特定函数

from模块名 import函数名

from pizza import make_piza
make_pizza(16,"peopperonic")
make_pizza(12,'mushroom','pepperoni','green peppers','extra cheese')

8.6.3使用as给函数指定别名

将函数进行重命名

from pizza import make_pizza as mp
mp(16,'people')
mp(12,'mushroom','pepperoni','green peppers','extra cheese')

8.6.4使用as给模块指定别名

通过给指定的简短的别名，让我们更轻松的调用模块中的函数。

import pizza as p
p.make_pizza(16,'people')
p.make_pizza(12,'mushroom','pepperoni','green peppers','extra cheese')

8.6.5导入模块中的所有函数

使用 *运算符可以让 Python导入模块的 所有函数

from pizza import *
make_pizza(16,'people')
make_pizza(12,'mushroom','pepperoni','green peppers','extra cheese')

九、类

9.1使用和创建类

self是自动创建的一个形参，可以访问自己创建的属性

class Dog():
    def __init__(self,name,age):
        self.name=name
        self.age=age
    def sit(self):
        print(self.name.title()+"is now sitting.")
    def roll_over(self):
        print(self.name.title()+"roll over!")

9.1.1根据类创建实例

class Dog():
   my_dog=Dog('willie',6)
   print("my dog name is"+my_dog.name.title()+".")
   print("my dog is"+str(my_dog.age)+"year ole ")

访问属性

class Dog():
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def sit(self):
        print(self.name.title() + "is now sitting.")
    def roll_over(self):
        print(self.name.title() + "roll over!")
my_dog=Dog('willie',6)
print("\n"+my_dog.name)

调用方法

class Dog():
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def sit(self):
        print(self.name.title() + "is now sitting.")
    def roll_over(self):
        print(self.name.title() + "roll over!")
my_dog=Dog('willie',6)
my_dog.sit()
my_dog.roll_over()

创建多个实例

class Dog():
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def sit(self):
        print(self.name.title() + "is now sitting.")
    def roll_over(self):
        print(self.name.title() + "roll over!")
my_dog=Dog('willie',6)
your_dog=Dog("lucky",3)
print("my dog name is"+my_dog.name.title()+".")
print("my dog is"+str(my_dog.age)+"years old")

9.2使用类和实例

class Car():
    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):
        print("This car has"+str(self.odometer_reading)+"miles on it")
my_new_car=Car('audi','a4',2016)
print(my_new_car.get_descriptive_name())
my_new_car.read_odometer()

9.2.3修改属性值

直接修改

class Car():
    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):
        print("This car has"+str(self.odometer_reading)+"miles on it")
my_new_car=Car('audi','a4',2016)
print(my_new_car.get_descriptive_name())
my_new_car.odometer_reading=23
my_new_car.read_odometer()

通过方法修改属性值

class Car():
    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 update_odometer(self,mileage):
        self.odometer_reading=mileage
    def read_odometer(self):
        print("This car has"+str(self.odometer_reading)+"miles on it")
my_new_car=Car('audi','a4',2016)
print(my_new_car.get_descriptive_name())
my_new_car.update_odometer(23)
my_new_car.read_odometer()

通过方法对属性值进行递增

class Car():
    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 update_odometer(self,mileage):
        self.odometer_reading=mileage
    def increment_odometer(self,miles):
        self.odometer_reading+=miles
    def read_odometer(self):
        print("This car has"+str(self.odometer_reading)+"miles on it")
my_used_car=Car('subaru','outback',2013)
print(my_used_car.get_descriptive_name())
my_new_car=Car('audi','a4',2016)
print(my_new_car.get_descriptive_name())
my_used_car.update_odometer(23)
my_used_car.read_odometer()

9.3继承

原有的类称为父类，新类称为子类
子类继承了父类所有的方法属性，同时还可以定义自己的属性和方法

9.3.1子类方法_init_()

class Car():
    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):
        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 roll back an  odometer!")
    def increment_odometer(self,miles):
        self.odometer_reading+=miles
class ElectricCar(Car):
    def __init__(self,make,model,year):
        super().__init__(make,model,year)
my_tesla=ElectricCar('tesla','model',2016)
print(my_tesla.get_descriptive_name())

9.3.3给子类定义属性和方法

class Car():
    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):
        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 roll back an  odometer!")
    def increment_odometer(self,miles):
        self.odometer_reading+=miles
class ElectricCar(Car):
    def __init__(self,make,model,year):
        super().__init__(make,model,year)
        self.battery_size=70
        
    def describe_battery(self):
        print("This  car has a "+str(self.battery_size)+"-kwh battery")
my_tesla=ElectricCar('tesla','model',2016)
print(my_tesla.get_descriptive_name())
my_tesla.describe_battery()

an odometer!")

def increment_odometer(self,miles):
    self.odometer_reading+=miles

class ElectricCar(Car):

def init(self,make,model,year):

super().init(make,model,year)

my_tesla=ElectricCar(‘tesla’,‘model’,2016)

print(my_tesla.get_descriptive_name())

### 9.3.3给子类定义属性和方法
```python
class Car():
    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):
        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 roll back an  odometer!")
    def increment_odometer(self,miles):
        self.odometer_reading+=miles
class ElectricCar(Car):
    def __init__(self,make,model,year):
        super().__init__(make,model,year)
        self.battery_size=70
        
    def describe_battery(self):
        print("This  car has a "+str(self.battery_size)+"-kwh battery")
my_tesla=ElectricCar('tesla','model',2016)
print(my_tesla.get_descriptive_name())
my_tesla.describe_battery()

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【免费分享编程笔记】Python学习笔记（二）