《Python核心编程》P21输入数值字符串→转整型

 

 

>>> num=input()
1234
>>> num
'1234'
>>> num=input(haha:)
SyntaxError: invalid syntax
>>> num=input('haha:')
haha:23
>>> num
'23'
>>> print(num)
23
'
>>> print(num)
23
>>> print('123:sdf',num)
123:sdf 23
>>> print('123:sdf:',num)
123:sdf: 23
>>> print('123:sdf: ',num)
123:sdf:  23
>>> print('zhuanzhengxing',int(num))
zhuanzhengxing 23
>>> print(int(num))
23
>>> print(int(num)*2)
46
>>> print('zhuanzhengxing',int(num)*2)
zhuanzhengxing 46
>>> print('zhuanzhengxing%d',int(num)*2)
zhuanzhengxing%d 46
>>> print('%d',int(num)*2)
%d 46
>>> print(%d,int(num)*2)
SyntaxError: invalid syntax
>>> print(%d%int(num)*2)
SyntaxError: invalid syntax
>>> print('%d'%int(num)*2)
2323
>>> # #前有%d，后用的逗号，没用%：%d当做字符输出了
>>> print(%int(num)*2)
SyntaxError: invalid syntax
>>> print('zhuanzhengxing%d'%int(num)*2)
zhuanzhengxing23zhuanzhengxing23
>>>  print('zhuanzhengxing'%int(num)*2)
 
SyntaxError: unexpected indent
>>> print('zhuanzhengxing'%int(num)*2)
Traceback (most recent call last):
  File "<pyshell#31>", line 1, in <module>
    print('zhuanzhengxing'%int(num)*2)
TypeError: not all arguments converted during string formatting
>>> #后面有% 没用逗号，而前面没有%，错误

 

原图：

>>> num=input('n:')
n:1234
>>> print('sdf:',n)
Traceback (most recent call last):
  File "<pyshell#72>", line 1, in <module>
    print('sdf:',n)
NameError: name 'n' is not defined
>>> print('sdf:',num)
sdf: 1234
>>> print('sdf:',int(num))
sdf: 1234
>>> print('sdf:',int(num)*2)
sdf: 2468
>>> print('sdf:%d',int(num)*2)     #前有%d，后用的逗号，没用%：%d当做字符输出了
sdf:%d 2468
>>> print('sdf:%d'%int(num)*2)
sdf:1234sdf:1234
>>> print('sdf:%d'%int((num)*2)))
SyntaxError: invalid syntax
>>> print('sdf:%d'%(int((num)*2)))
sdf:12341234
>>> print('sdf:%d'%(int(num)*2))
sdf:2468
>>> 
>>> print('sdf:'%int(num)*2)      #后面有% 没用逗号，而前面没有%，错误
Traceback (most recent call last):
  File "<pyshell#84>", line 1, in <module>
    print('sdf:'%int(num)*2)
TypeError: not all arguments converted during string formatting
>>> print('sdf:'%(int(num)*2))
Traceback (most recent call last):
  File "<pyshell#85>", line 1, in <module>
    print('sdf:'%(int(num)*2))
TypeError: not all arguments converted during string formatting
>>> 

 

 

#int（num）没括号不行

>>> print('sdf:%d'%int num*2)
SyntaxError: invalid syntax
>>> print('sdf:%d'%int num)
SyntaxError: invalid syntax
>>> 

原图： #int（num）没括号不行；    #字符串*2