How do I create an alias for a variable in Python?

Question

Normal way:

class A:
    def __init__(self):
        self.a.b.c = 10

    def another_method(self):
        self.a.b.c = self.a.b.c * 10

Aliased approach:

class A:
    def __init__(self):
        self.a.b.c = 10         
        alias self.aliased = self.a.b.c  # Creates an alias 

    def another_method(self):
        self.aliased = self.aliased * 10  # Updates value of self.a.b.c

How does one accomplish aliasing in Python? The reason I want to do this is to reduce cluttering due to long variable names. It's a multi threaded environment , so simply copying to a local variable will not work.

Answer 1

The solution to this is to use getter and setter methods - fortunately Python has the property() builtin to hide the ugliness of this:

class A:
    def __init__(self):
        self.a.b.c = 10

    @property
    def aliased(self):
        return self.a.b.c

    @aliased.setter
    def aliased(self, value):
        self.a.b.c = value

    def another_method(self):
        self.aliased *= 10  # Updates value of self.a.b.c

Generally, deeply nested attributes like self.abc are a sign of bad design - you generally don't want classes to have to know about objects that are 3 relationships away - it means that changes to a given item can cause problems throughout your code base. It's a better idea to try and make each class deal with the classes around it, and no further.

Answer 2

Python doesn't copy anything implicity, it only stores references so it will work no matter which environment you're in.

# this creates a list and stores a *reference* to it:
really_really_long_variable_name = [] 
# this creates another new reference to the *same list*. There's no copy.
alias = really_really_long_variable_name

alias.append('AIB')
print really_really_long_variable_name

You'll get ['AIB']