I want use “isinstance” to judge what type object people input from keyboard

Question

This is my code

num = input()
if  not isinstance(num,int):
    print("wrong input")
    num = input()

However if I type letters from keyboard,the computer gives this error：

please input a num
q
Traceback (most recent call last):
File "ex11.py", line 8, in <module>
  num = input()
  File "<string>", line 1, in <module>
NameError: name 'q' is not defined

what version of Python are you using? – ha9u63a7 Jan 25 '15 at 13:17 — ha9u63a7, Jan 25 '15 at 13:17
Thank for your help,I think the problem has been resolved. – Isaac Jan 25 '15 at 15:01 — Isaac, Jan 25 '15 at 15:01

score 3 · Accepted Answer · answered Jan 25 '15 at 13:14

In Python2, input immediately tries to eval the input. You should use raw_input to get a string. See the documentation.

It would also be more pythonic just to try to convert the user input to whatever format you need and handle exceptions that might occur:

inp = raw_input("enter a number:")
try:
  a = int(inp)
except ValueError:
  print "Could not convert input to int"

I want use “isinstance” to judge what type object people input from keyboard

1 Answers1