for Example if I create a class Point.
class Point:
def__init__(self, x, y):
self._x = x
self._y = y
and
class Point:
def__init__(self, x, y):
self.x = x
self.y = y
what is the difference in the use of self._x and just self.x.
The single underscore is just a naming convention to state that the property should be considered "semi-private" (similarly double underscore means "private"), but it doesn't have a semantic difference: both versions of the code should behave exactly the same. According to PEP-8:
_single_leading_underscore: weak "internal use" indicator. E.g.from M import *does not import objects whose name starts with an underscore.
single_trailing_underscore_: used by convention to avoid conflicts with a Python keyword.
__double_leading_underscore: when naming a class attribute, invokes name mangling (inside classFooBar,__boobecomes _FooBar__boo).
__double_leading_and_trailing_underscore__: "magic" objects or attributes that live in user-controlled namespaces. E.g.__init__,__import__or__file__. Never invent such names; only use them as documented.
If, for some reason, you have a variable prefixed by an underscore and it is acceptable to publicly access this variable, then it is a good practice to include the name of this variable in your module's __all__ list. This serves as a form of in-code documentation.
