How to create functors?

[Jan Kaliszewski]

Dnia 18-08-2009 o 22:51:19 Robert Dailey <rcdailey at gmail.com> napisał(a):

> The example I gave earlier is a bit contrived, the real example
> fundamentally requires a lambda since I am actually passing in local
> variables into the functions the lambda is wrapping. Example:
>
> def MyFunction():
>   localVariable = 20
>   CreateTask( lambda: SomeOtherFunction( localVariable ) ) # CreateTask
> () executes the functor internally

Lambda in Python is a sintactic sugar for some simple situations. But you
*always* can replace it with def, e.g.:

  def MyFunction():

      localVariable = 20
      def TaskFunction():
          SomeOtherFunction(localVariable)

      CreateTask(TaskFunction)

If we say about You can also use functools.partial:

  import functools

  def MyFunction():

      localVariable = 20
      CreateTask(functools.partial(SomeOtherFunction, localVariable)

...which (especially) makes sense if passed function is supposed to be
callend many times.

> This is more or less like the real scenario I'm working with. There
> are other (more personal) reasons why I prefer to avoid 'def' in this
> case. I want to keep the functor as central to the code that needs it
> as possible to improve code readability.

IMHO def is mostly more readable (see my previous mail...).

> Thanks for the help everyone. I guess in Python 3.0 the print()
> function will not require the import from __future__ to work in this
> particular case?

Print as a function is a standard feature of Py 3.x so it doesn't
require it (see: http://docs.python.org/3.1/whatsnew/3.0.html ).

Regards,
*j

-- 
Jan Kaliszewski (zuo) <zuo at chopin.edu.pl>