python学习_常用语句

1.变量

 1 name='hu qihang'                     #变量名应为英文，方便阅读
 2 name_of_gf='chen ye'                 #多个单词用下划线隔开
 3 名字='hu qihang'                      #变量名可以是中文
 4 NAME='hu qihang'                     #常量用大写，值是可变的，只是告诉你不要变
 5 print(name,name_of_gf,名字,NAME,sep='\n')

2.打印

 sum='''
 name='hu qihang'
 名字='hu qihang'
 NAME='hu qihang'
 '''                                  #三引号可以多行输出，单独使用为注释
 print(sum)

3.字符串格式化

3.1 %s

 name=input('your name:')             #用户输入input，输入的默认是字符串
 age=input('your age:')
 job=input('your job:')
 info='''
 ------info of %s-----
 Name:%s
 Age:%s
 Job:%s
 '''%(name,name,age,job)              #字符串格式化，%s字符串占位符，%d整型占位符，%f浮点型占位符，单一一个%s，可以直接%变量
 print(info)

3.2 format

3.2.1 format

 name=input('your name:')
 age=input('your age:')
 job=input('your job:')
 info='''
 ------info of {Name}-----
 Name:{Name}
 Age:{Age}
 Job:{Job}
 '''.format(Name=name,Age=age,Job=job)            #可以赋参数也可以不赋，不赋参数的话要按顺序写变量
 print(info)

3.2.2 format_map

 info='my name is {name},i am {years} old'
 print(info.format_map({'name':'huqihang','years':''}))      #括号里面是字典

4.getpass

 import getpass

 username=input('your username:')
 password=getpass.getpass('your password:')      #getpass输入时是秘文，在pycharm中不好用，

 print(username,password)

5.条件

5.1 if-else

 _username='huqihang'
 _password='123abc'
 username=input('your username:')
 password=input('your password:')
 if username==_username and password==_password:
     print('welcome user {Name} login!'.format(Name=username))
 else:
     print('invalid username or password!')

5.2 elif

 age_of_huqihang=23
 guess_age=int(input('guess age:'))
 if guess_age==age_of_huqihang:
     print('yes')
 elif guess_age>age_of_huqihang:
     print('smaller')
 else:
     print('bigger')

6.循环

6.1 while

6.1.1 三次机会猜数字

 age_of_huqihang=23
 count=1
 while count<4:
     guess_age=int(input('guess age:'))
     if guess_age==age_of_huqihang:
         print('yes')
         break
     elif guess_age>age_of_huqihang:
         print('smaller')
     else:
         print('bigger')
     count=count+1
 else:
     print('you have tried too many times!')

6.1.2 任意次机会猜数字

 age_of_huqihang=23
 count=1
 while count<4:
     guess_age=int(input('guess age:'))
     if guess_age==age_of_huqihang:
         print('yes')
         break
     elif guess_age>age_of_huqihang:
         print('smaller')
     else:
         print('bigger')
     count=count+1
     if count==4:
         continue_try=input('do you want to guessing.y/n')
         if continue_try=='y':
             count=1
         else:
             print('lost!')

6.2 for

6.2.1三次机会猜数字

 age_of_huqihang=23
 for i in range(3):
     guess_age=int(input('guess age:'))
     if guess_age==age_of_huqihang:
         print('yes')
         break                             #结束当前循环。多重循环时，结束当前循环，并不是结束所有循环
     elif guess_age>age_of_huqihang:
         print('smaller')
     else:
         print('bigger')
 else:                                     #for循环的else是执行完循环以后就运行else语句，如果break了，就跳出for不执行else
     print('you have tried too many times!')

6.2.2步长

  for i in range(0,10,2):         #从0到10，不包括10，2是步长，打印一个跳一个，默认是1

  2     print(i)  

6.3 break和continue

6.3.1 break

 for i in range(0,10):
     if i<3:
         print(i)
     else:
         break                             #结束当前循环
     print('oops')

6.3.2 continue

 for i in range(0,10):
     if i<3:
         print(i)
     else:
         continue                         #跳出本次循环，继续下次循环
     print('oops')