What is the meaning of double leading underscore (_) and single leading underscore () before the Python method in a class? For example:
class A: def singleunderscored_method(): pass
def __double_underscored_method():
pass
Hi @dEybid
Single leading underscore means that the method is for internal use inside method only. Also, if you will perform such import:
from A import *
This wouldn't import methods with the leading underscore. Nevertheless, if you need to use this method, you can import it explicitly and use. But it is not a good habit. In other words, a single underscore is like a caution that this method is internal and should be used only inside the class.
Double underscore is a stronger indicator that the method should be used only inside the given class. Double underscore performs so-called name mangling. To call such a method you will need to use a weird construction:
A._A__double_underscored_method()
Hi,
Single leading underscore is used to define an internal method, while double underscores - to define a private method. My recommendation is to avoid using private methods. When you want to show that this method shouldn't be used outside, just mark it as internal. Private methods could cause a lot of unexpected nasty things, especially if your program becomes complex, and when many programmers work together to develop it.
Regards.
Maybe you will be interested in this material about how underscores are used in Python: https://hackernoon.com/understanding-the-underscore-of-python-309d1a029edc
Spoiler: It is not only for internal and private methods definitions, there are also many other interesting cases.
Wow, it is very interesting! Thank you all!
Just drop us an email to ...
Show more 
Log in with Google