python学习——第一个python代码/变量/编码/用户交互/判断/循环

一、第一个python代码

#！/usr/bin/env python
 
print("hello world")

• python要注意缩进

 

二、变量

#！/usr/bin/env python

name="wang"

print("This is ", name)

　　

三、编码

ASCII　　255　　1bytes

　　-->1980　　gb2312　　7000+

　　　　-->1995　　GBK1.0　　20000+

　　　　　　-->2000　　GB18030　　27000+

　　　　-->199*　　unicode　　2bytes

　　　　　　-->utf-8　　en:1byte　　zh:3bytes

 

四、注释

#单行注释

‘’‘多
行
注
释’‘’

　　

五、用户交互

#！/usr/bin/env python
 
username=input("username:")
password=input("password:")

print(username, password)

　　

#！/usr/bin/env python
 
name=input("name:")
password=input("password:")

info='''
---info of %s---
name:%s
password:%s
'''% (name,name,password)
#以上除了%s还可用%d、%f

print(info)

　　

#！/usr/bin/env python
 
name=input("name:")
password=input("password:")

info = '''
---info of {_name}---
name:{_name}
password:{_password}
'''.format(_name=name,
		   _password=password)

print(info)

　　

五、判断

#！/usr/bin/env python
 
_username = 'wang'
_password = '123'
username = input("username:")
password = input("password:")

if _username == username and _password == password:
	print("Welcome {name}".format(name=username))
else:
	print("Invalid username or password!")

• python中的elseif应写为elif

 

六、循环

#！/usr/bin/env python
 
age = 18

count = 0
while count <3:
    guess_age = int(input("guess age:") )
    if guess_age == age :
        print("yes, you got it. ")
        break
    elif guess_age > age:
        print("think smaller...")
    else:
        print("think bigger!")
    count +=1
else:
    print("you have tried too many times..")

　　

#！/usr/bin/env python
 
age = 18

for i in range(3):
    guess_age = int(input("guess age:") )
    if guess_age == age :
        print("yes, you got it. ")
        break
    elif guess_age > age:
        print("think smaller...")
    else:
        print("think bigger!")
else:
    print("you have tried too many times..")

• continue:跳出本次循环
• break:跳出整个循环