[Tutor] Applications/examples of some advanced Py features, p lease !

Tue Jan 7 16:11:22 2003

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>  Can anyone please give some examples / applications of the use of the
following advanced  
>  (advanced to me, at least :-) features of Python :

1. lambda 

I cover lambdas in my Functional Programming topic on my online tutor...

2. nested functions - a little info was given by Danny in reply to my
earlier post on local-static  
 variables, but I would like more. 

Its just a function defined inside another function, it can either be a
helper function for the "parent" 
one or it can be a function that is returned by the parent in a similar way
to the lambda construct
(see above). This latter style of programming is powerful in a few areas and
replaces lambdas
in many cases.

3. Thoughts on implementing Interfaces in Py - a la Java interfaces. 

You can do it since an interface is just a class with empty method
definitions. 
What Python won't do is force you to provide definitions though.

However there is little or no need for interfaces in Python since it support
full multiple 
inheritance and its dynamic nature makes the use of interfaces redundant in
most cases anyway.

Python effectively checks the interface of any object when it uses it.

 > I am planning to write a game-playing program in Py which will have
features somewhat AI - ish.  

Thats fine, but you shlouldn't need interfaces. THe other features may be
useful.

>   - in what way their use makes code simpler, or maybe makes code possible

>  that could not be written otherwise ('possible' in practical terms - I'm
- vaguely - aware  
> of the fact that all languages are supposed to be theoretically
'Turing-equivalent' or  
>  some such term - but what I mean is that if something is going to take a
huge  
>  amount more code in some other language, or jumping through hoops, then  
>  I don't call it practically equivalent). 

Languages are practically equivalent if they can do the same jobs. There may
be good 
reasons to write reams more code - like performance! But for most purposes
each 
language has some things it is better at. Python is not the best AI language
but its 
better than, say, C++ or Java.

IMHO of course! :-)

Alan g. 
Author of the Learn to Program website 
http://www.freenetpages.co.uk/hp/alan.gauld/
<http://www.freenetpages.co.uk/hp/alan.gauld/>

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<DIV>&gt; 
&nbsp;Can anyone please give some examples /&nbsp;applications of 
the use of the following advanced&nbsp;&nbsp;</DIV>
<DIV>&gt; 
&nbsp;(advanced to me, at least :-) features of Python :</DIV>
<BLOCKQUOTE 
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid">
 1. lambda&nbsp;</BLOCKQUOTE>
I cover 
lambdas in my Functional Programming topic on my online 
tutor...
<BLOCKQUOTE 
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid">
 2. nested functions -&nbsp;a little info was given by Danny in reply to my 
 earlier post on local-static&nbsp;&nbsp; &nbsp;variables, but I would like more.&nbsp;</BLOCKQUOTE>
Its just 
a function defined inside another function, it can either be a helper function 
for the "parent" one or it can be a function that is returned by 
the parent in a similar way to the lambda construct (see above). This latter 
style of programming is powerful in a few areas and replaces lambdas in many 
cases.
<BLOCKQUOTE 
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid">
 3. Thoughts on implementing Interfaces in Py - a la Java interfaces.&nbsp;</BLOCKQUOTE>
You can 
do it since an interface is just a class&nbsp;with empty method definitions. What Python won't do is 
force you to provide definitions though.
However 
there is little or no need for interfaces in Python since it support full 
multiple inheritance and its dynamic nature makes the use of interfaces 
redundant in most cases anyway.
Python 
effectively checks the interface of any object when it uses 
it.
&nbsp;&gt;&nbsp;I am planning to write a game-playing 
program in Py which will have features somewhat AI - ish.&nbsp;&nbsp;
Thats 
fine, but you shlouldn't need interfaces. THe other features may be 
useful.
&gt; 
&nbsp;&nbsp;- in what way their use makes code simpler, or maybe 
makes code possible&nbsp;&nbsp; &gt; &nbsp;that could not be 
written otherwise ('possible' in practical terms - I'm - vaguely - 
aware&nbsp;&nbsp; &gt;&nbsp;of the fact that all languages are 
supposed to be theoretically 'Turing-equivalent' or&nbsp;&nbsp; &gt; 
&nbsp;some such term - but 
what I mean is that if something is going to take a huge&nbsp;&nbsp; &gt; 
&nbsp;amount more code in 
some other language, or jumping through hoops, then&nbsp;&nbsp; &gt;&nbsp; 
I don't call it practically equivalent).&nbsp; 
Languages are practically equivalent if they can do the same jobs. There 
may be good reasons to write reams more code - like performance! But 
for most purposes each language has some things it is better at. Python is 
not the best AI language but its better than, say, 
C++ or Java.
IMHO of 
course! :-)
Alan g. Author of the Learn to Program website <A target=_blank 
href="http://www.freenetpages.co.uk/hp/alan.gauld/">http://www.freenetpages.co.uk/hp/alan.gauld/</A> 

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