Python学习笔记1

#1.变量和简单数据类型
print("hello python world!")

message = "hello python world!"
print(message)
print(message.title()) #首字母大写
print(message.uper())  #全部大写
print(message.lower()) #全部小写

full_name = "lin" + "hai" #合并字符串
print("Hello, " + full_name.title() + "!")
print("John Q. %s10s" % ("Man","Public")) #%是针对字符串的格式说明符，10表示长度为10的字符，如果长度小于10则该字符串前会加入相应数量空格
print("\tPython") #制表符
print("Languages:\nPython\nC\nJavaScript")

type(12j+1) #序数尾部都有一个字母j
name = "lin hai "
name.rstrip() #删除末尾空白
name.lstrip() #删除开头空白
name.strip()  #删除两端空白

age = 23
message = "Happy" + str(age) + "rd Birthday!" #str()将整数用作字符串
print(message)

#2.列表
shapes = ['a', 'b','c','d','e']
print(shapes[0])             #打印第1个元素
print(shapes[1].title())     #打印第2个元素，且首字母大写
print(shapes[-1])            #打印最后一个元素
print(shapes[-2])            #打印倒数第二个元素
shapes.append('granda') #添加元素
print(shapes)

e = []
e.append("e1")#添加元素
e.append("e2")
e.extend("e3","e4","e5") #同时添加多个元素
 
shapes.insert(0,"bb") #在第1个位置插入元素
print(shapes)

del shapes[0] #删除第一个元素
print(shapes)

poped_shapes = shapes.pop() #删除列表末尾的元素
print(shapes)
print(poped_shapes)

first_shapes = shapes.pop(0) #删除第1个元素

shapes.remove("e") #删除e, 但remove只删除第1个指定的值
print(shapes)

cars = ['bmw','audi','bench','toyota','subaru']
cars.sort() #永久性排序
print(cars) 

cars.sort(reverse = True) #逆序
print(cars)

print(sorted(cars)) #临时排序
print(cars)

cars.reverse() #永久性地反转列表元素的排列顺序

len(cars) #列表的长度

for car in cars:
print(car)

for value in range(1,6): #打印1-5
print(value)

numbers = list(range(1,6))
print(numbers)

min(numbers)
max(numbers)
sum(numbers)

squares = [value**2 for value in range(1,11)] #1到10的平方
print(squares)

print(squares[0:3]) #打印0,1,2的元素
print(squares[:4])  #打印0,1,2,3的元素
print(squares[2:])  #打印从第3个元素开始到末尾的所有元素
print(squares[-3:]) #打印最后三个元素

for value in squares[:3]:
print(value)

squares1 = squares[:] #复制列表
print(squares1)

squares2 = squares #是将副本存储到squares2中，因此二者指向同一个列表

#元组：不可变的列表
dimensions = (200,50) #定义元组,使用的是圆括号而不是方括号
print(dimensions[0])
#dimensions[1] = 10   #试图修改元组是被禁止的

#3.if语句
#例1
for car in cars:
if car == 'bmw':
print(car.upper())
else: 
print(car.lower())

car = 'Audi'
car == 'audi' #返回的是False，区分大小写
car.lower() == 'audi'
if car !="audi" :
print("car is title")

age = 19
age <= 21 and age >= 15
age <20 or age >19 

car = 'bench'
car in cars     #检查特定值是否包含在列表中
car not in cars #检查特定值是否不包含在列表中

#例2
if age < 18:
print("You are so young!")
else if age < 25:
print("You are young!")
else:
print("Hello uncle!")

#例3
requested_toppings = []
if requested_toppings: #确定列表非空
for requested_topping in requested_toppings:
print("Adding" + requested_topping + ".")
print("\nFinished making your pizza")
else:
print("Are you sure you want a plain pizza?")

#4.字典
alient = {'color':'green','points':5} #颜色键值对和点数键值对
print(alient['color'])
print(alient['points'])

alient['x_position'] = 0  #新增键值对
alient['y_position'] = 25 
print(alient)

alient['color'] = 'yellow' #修改字典中的值

del alient['points'] #删除键值对

alient1 = {} #创建空字典
alient1['color'] = 'green'
alient1['points'] = 5

#例1
user = {'username':'hy','first':'huang','last':'ying'}
for key,value in user.items(): #遍历键值对
print("\nkey:" + key)
print("value:" + value)

for item in user.keys():       #遍历键
print(item.upper())

for item in sorted(user.keys()):
print(item.upper())

for name in user.values():     #遍历值
print(name.title())

for name in set(user.values()):#用集合，使得每个元素独一无二
print(name.title())

#例2
alient_0 = {'color':'green','points':5}
alient_1 = {'color':'red','points':10}
alient_2 = {'color':'yellow','points':15}
alients = [alient_0, alient_1, alient_2]  #字典列表

for alient in alients:
print(alient)

alients = []
for alient_number in range(30):  
new_alient = {'color':'green','points':alient_number}
alients.append(new_alient)

for alient in alients[:5]:  #显示前五个
print(alient)
print("...")
print("Total number of alients:" + str(len(alients)))

#例3
pizza = {'crust':'thick', 'toppings':['mushrooms','extra cheese']} #字典中存储列表
for topping in pizza['toppings']:
print("\t" + topping)

#例4
favorate_languages = {
                      'jen':['python','ruby'],
                      'sarah':['c'],
                      'edward':['ruby','go'],
                      'phil':['python','haskell'],
            }
for name,languages in favorate_languages.items():
print("\n" + name.title() + "'s favorate languages are:")
for language in languages:
print("\t" + language.title())

#例5
users = {
        'aeinstein':{
           'first':'albert',
'last':'einstein',
'location':'princeton',
           },
'mcurie':{
       'first':'marie',
'last':'curie',
'location':'paris',
       },
        }

for username,user_info in users.items():
print("\nUsername:" + username)
full_name = user_info['first'] + user_info['last']
location = user_info['location']
print("\tFullname" + full_name.title())
print("\tLocation:" + location.title())

#5.用户输入和while循环
message  = input("Tell me something, and I will repeat it back to you:")
print(message)

age = input("How old are you?") #默认解读为字符串
age = int(age) #使用int()将数字的字符串转换为数值
age >= 18

number = input("Enter a number, and I'll tell you if it's 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.")

#例1
current_number = 1
while current_number <=5:
print("current_number")
current_number +=1
if current_number == 3:
break

#例2
number = 0
while number < 10:.0.
number +=1
if number % 2 ==0:
continue
print(number)

#例3
unconfimed_users = ['alice','brian','candace']
confirmed_users = []
while unconfirmed_users:
current_user = unconfimed_users.pop() #删除列表末尾的元素
print("Verifying user:" + current_user.title())
confirmed_users.append(current_user)
print("\nThe following users have been confirmed:")
for confirmed_user in confirmed_users:
print(confirmed_user.title())

#简单匿名函数lambda,filter
filter_me = [1,2,3,4,5,6,7,8]
result = filter(lambda x: x%2==0,filter_me)
print(*result)

#短路循环：Map
map_me = ['a','b','c','d','e','f','g']
result1 = map(lambda x:"The letter is %s \n"%x,map_me)
print(*result1)

#列表解析
all = [1,2,3,4,5,6,7,8,9,10]
print([x for x in all if x%2==0])

#例4
pets = ['dog','cat','dog','rabbit','dog']
while 'dog' in pets:
pets.remove('dog')