Path: csiph.com!usenet.pasdenom.info!news.etla.org!feeder.erje.net!eu.feeder.erje.net!newsfeed.xs4all.nl!newsfeed2a.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Date: Fri, 14 Nov 2014 23:02:04 +0000
From: MRAB <python@mrabarnett.plus.com>
User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0
MIME-Version: 1.0
To: python-list@python.org
Subject: Re: Array of Functions
References: <42b534f0-aeef-411f-80c5-db5d20c80b55@googlegroups.com>
In-Reply-To: <42b534f0-aeef-411f-80c5-db5d20c80b55@googlegroups.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.15833.1416006313.18130.python-list@python.org>
Lines: 57
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:80792

On 2014-11-14 22:17, Richard Riehle wrote:
> In C, C++, Ada, and functional languages, I can create an array of
> functions, albeit with the nastiness of pointers in the C family.
> For example, an array of functions where each function is an active
> button, or an array of functions that behave like formulae in a
> spreadsheet.  I am finding this a bit challenging in Python.
>
> Example:
>
>              r1c1   r1c2  r1c3
>              r2c1   r2c2  r2c3
>              r3c1   r3c2  r3c3
>
> where r1 is row 1 and c1 is column 1.  Suppose I want an array where
> the colum three is a set of functions that operates on the other two
> columns, depending on the values I set for those rows and columns?
> As noted, I can do this pretty easily in most languages (well, except
> for Java which does not support any kind of functional programming
> capability), even if I have to use pointers.
>
> I think my difficulty is related to the REPL nature of Python.
> However, I am sure some clever Pythonista has found a way to do
> this.
>
> Thanks in advance for any suggestions,
>
In C, you're not creating an array of functions, but an array of
_pointers_ to functions.

In Python, we don't have pointers, but we do have references.

For example, you can define a function:

 >>> def my_func():
...     print('my_func called')
...

The name of the function is just a reference to that function:

 >>> print(my_func)
<function my_func at 0x0000000002CBCBF8>

You call it using (...):

 >>> my_func()
my_func called

You can store the reference in a list or bind another name to it:

 >>> func_by_another_name = my_func

And call it by that other name:

 >>> func_by_another_name()
my_func called

Does that help?