[Tutor] How to run a .py file or load a module?

[Norman Khine]

On Mon, Apr 27, 2009 at 12:07 AM, Sander Sweers <sander.sweers at gmail.com> wrote:
> 2009/4/26 Dayo Adewunmi <contactdayo at gmail.com>:
>> I'm looking at recursion in "Think Python", and this is the bit of code:
>>
>> #!/usr/bin/env python
>>
>> def countdown(n):
>>       if n <= 0:
>>               print 'Blastoff!'
>>       else:                 print n
>>               countdown(n-1)
>>
>>
>> I've typed that in vim and saved as countdown.py, but I'm not sure how to
>> run it.
>>
>> However with this particular function that requires an argument, I'm not
>> sure how to run it.
>>
>> I've had to type it out in the python prompt and then
>> call
>> the function with an argument. That works, naturally.
>>
>> I've also tried this:
>>
>>       >>>import countdown
>>       >>>countdown(10)
>
> When you import it lile this the function countdown is part of the
> module countdown. So you call it like countdown.countdown(10). Or
> import it like "from countdown import countdown" and then your example
> will work.
>
>> but this is the error I get:
>>
>>       Traceback (most recent call last):
>>         File "<stdin>", line 1, in <module>
>>       NameError: name 'countdown' is not defined
>>
>> How can I
>>
>> a) Open my shell, and do something like: $ python countdown.py   but have it
>> take an argument and pass it to the function, and execute.
>
> Look at sys.argv which returns a list with the first value being the
> script name and the second are the command line argument(s).
> http://docs.python.org/library/sys.html
>
>> b) Import the function in the interactive interpreter, and call it like so:
>>
>>       countdown(10)
>>
>> without getting the abovementioned error.
>
> See above.
>
> The script would then look like:
>
> #!/usr/bin/env python
>
> import sys
>
> times = int(sys.argv[1]) # The argument given on the command line
>
> def countdown(n):
>    if n <=0:
>        print 'Blast off!'
>    else:
>        countdown(n-1)
>
> countdown(times)

Don't forget to add:

if __name__ == '__main__':
    launchme(times)

>
> Greets
> Sander
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
>