input vs. raw_input: Python Interactive Shell Application?

Question

I was working off of the answer in this question: Python Interactive Shell Type Application

My code looks like this

def main():
  while True:
    s = input('> ')

    if s == 'hello':
      print('hi')

    if s == 'exit':
      break

if __name__ == "__main__":
  main()

If I run it, and type hello, I get

  File "<string>", line 1, in <module>
NameError: name 'hello' is not defined

How should I be listening for text, and calling different functions based on the result?

You need raw_input, not input (the latter evaluates what you type as a Python expression). — Gareth Rees
– Gareth Rees, Commented Apr 5, 2013 at 18:13

kindall · Accepted Answer · 2013-04-05 18:14:07Z

5

You're running it under Python 2.x, where input() actually evaluates what you type as a Python expression. Thus, it's looking for a variable named hello, and, since you haven't defined one, it throws the error. Either use Python 3.x, or use raw_input().

From the parentheses in your print I assume you intended to run it under Python 3.x.

answered Apr 5, 2013 at 18:14

kindall

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1 Comment

rob-gordon Over a year ago

Thank you! I think I would rather force users to call defined variables, but how do I write a my own error message if they input something that is undefined?

ThinkCode · Accepted Answer · 2013-04-05 18:34:33Z

1

if s == 'hello':
  print('hi')

elif s == 'exit':
  break

else:
  print('Undefined input')

This should take care of undefined user input.

answered Apr 5, 2013 at 18:34

ThinkCode

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2 Comments

rob-gordon Over a year ago

This seems to work when using raw_input, but when using input python still throws a NameError rather than just printing 'Undefined Input'

ThinkCode Over a year ago

Why don't you use argparse - that is a better way of doing it imo? stackoverflow.com/questions/7427101/…

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