python logic

[eth0]

Era el Fri, 1 Sep 2017 06:30:43 -0700 (PDT) en comp.lang.python,
cuando de repente SS
dijo lo siguiente acerca de
python logic:

>  Check out the following simple code:
> 
>  #!/bin/python
> 
>  print "1 - echo 1"
>  print "2 - echo 2"
> 
>  answer = input("Enter your choice - ")
> 
>  if answer == 1:
>    print "1"
>  elif answer == 2:
>    print "2"
>  else:
>    print "Invalid choice!"
> 
> 
>  The else statement noted above works fine for numeric values other
>  then 1 or 2.  But if a user types in alphanumeric data (letters) into
>  this, it blows up.  Check out the following:
> 
>  [root at ansi ~]$ ./trash
>  1 - echo 1
>  2 - echo 2
>  Enter your choice - 3
>  Invalid choice!
> 
>  [root at ansi ~]$ ./trash
>  1 - echo 1
>  2 - echo 2
>  Enter your choice - r
>  Traceback (most recent call last):
>    File "./trash", line 6, in <module>
>      answer = input("Enter your choice - ")
>    File "<string>", line 1, in <module>
>  NameError: name 'r' is not defined
> 
>  I would expect the same behavior from both runs.  Why does Python
>  differ in the way it treats a character in that program?  Finally,
>  how to accomodate for such (how to fix)?
> 
>  TIA

In Python 2, the input() function evaluates whatever you enter in the
prompt. In your case, Python is trying to evaluate 'r' as if it was
a variable or something. Use the raw_input() function instead.

However, note that if you ever want to run your script with Python 3
you'll have to switch back to using input(), which does exactly the
same as Python 2's raw_input().