简单的python代码中的NameError

Question

This is a simple palindrome checker. The code works for numbers, but not strings.

x = str(input("Enter a number: "))
if x == x[::-1]:
    print x + " is a palindrome!"
else:
    print x + " is not a palindrome!"

When I try inputting a string, I get this error:

  File "palindrome.py", line 1, in <module>
    x = str(input("Enter a number: "))
  File "<string>", line 1, in <module>
NameError: name 'abba' is not defined

Answer 1

It seems you are using Python 2.x!

Please use raw_input for keyboard input. This always returns a string, so there is no need to cast/convert.

In Python 2.x input tries to evaluate the text entered as Python, and you never defined abba, so it will cause a NameError

See docs for more.

Answer 2

Where you input some numbers.For example,"Enter a number: 1221".you can get

x=str(1221)

it's rigth.

But, "Enter a number: abba".you can get

x=str(abba)

it's wrong.Beacuse the "abba" is not string, and is not defined.

you can try "Enter a number: 'abba'", or use

raw_input('Enter a number:')

replace input("Enter a number: ") and You can get the results you want.

read more information on here