Deep vs. shallow copy?

[Steven D'Aprano]

On Thu, 13 Mar 2014 14:27:48 +0200, Marko Rauhamaa wrote:

> Roy Smith <roy at panix.com>:
> 
>>  Steven D'Aprano <steve+comp.lang.python at pearwood.info> wrote:
>>
>>> Because Python doesn't have true procedures
>>
>> What do you mean by "true procedure"? Are you just talking about
>> subroutines that don't return any value, i.e. fortran's SUBROUTINE vs.
>> FUNCTION?
> 
> Ah, the "no true procedure" argument:
> 
>  - No true procedure returns a value.
> 
>  - That's false. Python's procedures return None.

Are you trolling again? 

I'm sure that you know quite well that Python doesn't have a procedure 
type. It uses a single keyword, def, for creating both functions and 
functions-that-return-None.

We should all agree that functions-that-return-None are used for the same 
purpose as procedures, but they are still functions, and they have a 
return result, namely None. If you don't believe me, believe Python:

py> def func():
...     return 42
...
py> def proc():
...     pass
...
py> type(func)
<class 'function'>
py> type(proc)
<class 'function'>
py> repr(proc())
'None'

In languages with procedures, that last line would be an error (either at 
compile-time, or run-time) since a procedure wouldn't return anything to 
use as argument to repr. But I'm sure that you know that.


>  - They are not true procedures.

Correct. They are functions that return None, rather than a subroutine 
that doesn't have any return value at all. But I'm sure you know that.





-- 
Steven D'Aprano
http://import-that.dreamwidth.org/