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I want to know all Python built-in private variables such as __file__, __name__, and their purpose.
but I don't see the document of all Python built-in private variables in www.python.org.
I have know dir and vars.
So, how to find them?
340
The __name__ variable (two underscores before and after) is a special Python variable. It gets its value depending on how we execute the containing script. Sometimes you write a script with functions that might be useful in other scripts as well. In Python, you can import that script as a module in another script.
However, inside the class (myClass) we can access the private variables. In the hello() method, the __privateVar variable can be accessed (as shown above: “Private Variable value: 27”). So from the above example, we can understand that all the variables and the methods inside the class are public by the method.
The __module__ property is intended for retrieving the module where the function was defined, either to read the source code or sometimes to re-import it in a script.
In Python, there is no existence of “Private” instance variables that cannot be accessed except inside an object.
What do you say about:
>>> dir()
['__builtins__', '__doc__', '__name__', '__package__', 'f']
>>> [ i for i in dir() if i.startswith("__") and i.endswith("__")]
['__builtins__', '__doc__', '__name__', '__package__']
You can define an auxiliary function:
>>> def getprivates(obj):
return [i for i in dir(obj) if i.startswith("__") and i.endswith("__")]
and apply to any object reference even to dir() itself:
>>> getprivates(dir())
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__delslice__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getslice__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__setslice__', '__sizeof__', '__str__', '__subclasshook__']
The hidden attributes are sometimes referred to as magic methods (for objects) and for reference, I would check out the Python docs on the data model, which are fairly comprehensive and likely cover all of the attributes you're looking to find.
After you've learned the hidden attributes, you may know what you want to get, but hidden attributes may vary by implementation, so to abstract that away, use the inspect module:
import inspect
To get a lot of information:
inspect.getmembers(inspect)
To get the file and a bit more information on a module:
>>> inspect.getfile(inspect)
'/usr/lib/python2.7/inspect.pyc'
>>> inspect.getmoduleinfo(inspect.getfile(inspect))
ModuleInfo(name='inspect', suffix='.pyc', mode='rb', module_type=2)
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