[Tutor] constructors

[Erik Price]

On Thursday, April 11, 2002, at 03:14  PM, dman wrote:

> In either case, you can't
> return a value from __init__ -> the object already exists and is
> referenced by 'self', the __init__ just initializes the data in it.
> If the __init__ method completes, then the client gets the reference
> to the object.  You can return 'false' or 'self' or 'fubar', but the
> client will never see it.

Ah. This is very important -- I was thinking that if the constructor 
returned false, then the instance would not be created.  Thank you.

> The do_something function doesn't need to do anything special (like
> check a return value and propagate it by returning it) to not ignore
> error conditions.  The module-level code doesn't need to interrupt the
> flow of the code by checking a return value either, and can handle the
> same type of error from both functions identically (if it wants to).

This is nice.  In PHP, I often do such code as:

if (!$connect = mysql_connect($connection_parameters)) {
   die("Database connection failed");
}

if (!$result = mysql_query($sql, $connection_handle)) {
   die("SQL query failed");
}

etc etc.
It gets very repetitive, and makes the code look ugly.  But I hadn't 
realized that this "interrupts the flow of code".

Exceptions are sweet -- I take it that they are another Python-centric 
feature, that does not exist in C/C++/Java?


Erik