Simple Python Syntax Questions

[chipwhisperer]

Hey all,

would really appreciate some help with this:

1) I see in code that people will define subclasses like this:

def __init__(self, **config):
server = config.get('server', 'dnd')

what does the ** mean? I've also seen it as one asterisk. Or is that different?

2) i have also seen people define methods of classes with one underscore in front of the name and this is somehow special. why?

I know these may be basic questions, but I've never learned python formally and need to get on these.

Thanks to anyone who can help?

[Kakao]

Originally Posted by chipwhisperer

1) I see in code that people will define subclasses like this:

def __init__(self, **config):
server = config.get('server', 'dnd')

what does the ** mean? I've also seen it as one asterisk. Or is that different?

A parameter starting with ** means the function/method accepts named parameters that will be available as a dictionary:

>>> def f(**keywords):
...    for key in keywords:
...       print key, keywords[key]
...
>>> f(var1=1, var2=3)
var1 1
var2 3

When the parameter starts with a single * it means positional arguments are accepted:

>>> def f(*a_tuple):
...    for item in a_tuple:
...       print item
...
>>> f(1,7,'car')
1
7
car

Originally Posted by chipwhisperer

2) i have also seen people define methods of classes with one underscore in front of the name and this is somehow special. why?

It is a warning to other programmers that it is a private method and should not be used directly. It is not enforced by the interpreter.

[chipwhisperer]

Wow! What a great explanation! Thank you so much!