How do these Java concepts translate to Python?

[Ben Finney]

Ray <ray_usenet at yahoo.com> wrote:
> 1. Where are the access specifiers? (public, protected, private)

No such thing (or, if you like, everything is "private" by default).

By convention, "please don't access this name externally" is indicated
by using the name '_foo' instead of 'foo'; similar to a "protected".
Nothing in the language enforces this.

Recently, the language came to partially support '__foo' (i.e. a name
beginning with two underscores) as a pseudo-"private". It's just a
namespace munging though; sufficiently determined users can get at it
without much effort.

The attitude engendering this simplicity is "we're all consenting
adults here". If you have users of your modules and classes who won't
respect access restriction *conventions*, they're bad programmers
anyway, so there's not much the language can do to stop that.

> 2. How does Python know whether a class is new style or old style?
> E.g.:
> 
> class A:
>     pass

New-style classes are descended from class 'object'. Old-style classes
aren't.

Thus, your example above is an old-style class, as are any classes
that inherit only from that class.

To create a new-style class with no particular base functionality,
inherit from 'object' directly:

    class A(object):
        pass

> 3. In Java we have static (class) method and instance members. But
> this difference seems to blur in Python.

Class attributes and instance attributes are distinguished by the fact
that instance attributes are created when the instance is created
(typically, assigned within the __init__() method):

    class A(object):
        foo = 'Fudge'
        def __init__(self, bar):
            self.bar = bar

    wibble = A('Wibble')
    print wibble.foo, wibble.bar    # Fudge Wibble
    bobble = A('Bobble')
    print bobble.foo, bobble.bar    # Fudge Bobble

Instances of the 'A' class all share a 'foo' attribute, and each
instance has its own 'bar' attribute created separately (in the
__init__() method).

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Ben Finney <http://www.benfinney.id.au/>