reading help() - newbie question

[Colin J. Williams]

On 31-May-10 06:19 AM, Payal wrote:
> Hi,
> I am trying to learn Python (again) and have some basic doubts which I
> hope someone in the list can address. (English is not my first language and I
> have no CS background except I can write decent shell scripts)
>
> When I type help(something) e.g. help(list), I see many methods like,
> __methodname__(). Are these something special? How do I use them and why
> put "__" around them?
>
> One more simple query. Many times I see something like this,
> |      D.iteritems() ->  an iterator over the (key, value) items of D
> What is this iterator they are talking about and how do I use these
> methods because simly saying D.iteritems() does not work?
>
> Thanks a lot in advance.
> With warm regards,
> -Payal

Here is an extract from the docs for Python 2.6.5.

I hope that this clarifies things.

Colin W.

2.3.2. Reserved classes of identifiers
Certain classes of identifiers (besides keywords) have special meanings. 
These classes are identified by the patterns of leading and trailing 
underscore characters:

_*
Not imported by from module import *. The special identifier _ is used 
in the interactive interpreter to store the result of the last 
evaluation; it is stored in the __builtin__ module. When not in 
interactive mode, _ has no special meaning and is not defined. See 
section The import statement.

Note
The name _ is often used in conjunction with internationalization; refer 
to the documentation for the gettext module for more information on this 
convention.

__*__
System-defined names. These names are defined by the interpreter and its 
implementation (including the standard library); applications should not 
expect to define additional names using this convention. The set of 
names of this class defined by Python may be extended in future 
versions. See section Special method names.
__*
Class-private names. Names in this category, when used within the 
context of a class definition, are re-written to use a mangled form to 
help avoid name clashes between “private” attributes of base and derived 
classes. See section Identifiers (Names).