What object is _(underlined) before the name?

_: Writing with _name in the class is This is to inform the programmer that attribute or method is private. When import *, object whose name starts with _ is not imported. There is no other function.

__(Name Mangling):

The identifier whose name starts with more than one underscore will be replaced with the _classname__spam. So it's usually used to define a class-private instance, a class variable, a method, a global variable, and so on.

However, it is important to note that this mangling only serves to prevent accidental access to private, It is still possible to access/modify private if you decide.

class foo():
    def __init__(self):
        self.__myPrivateInt = 3

    def printPrivate(self):
        print(self.__myPrivateInt)

myfoo = foo()
#printmyfoo.__myPrivateInt #DirectAccess -> Error

mydict = myfoo.__dict__
mydict['_foo__myPrivateInt'] = 4 #___myPrivateInt changed
myfoo.printPrivate()

Result: 4