如何在Python中为多个变量分配相同的值

Question

I have a question about Python, which I am kinda new to. Let's assume I want to assign a 5x5 matrix to 10 different variables. I searched across the board, and what I found was this:

a, b, c, d, e = myMatrix

That is all good, but in Python, this means that when I change a, I also change the values of the other variables, because they all come down to the same memory adress if I got this correctly.

My question: Is there a fast way of assigning myMatrix to multiple Variables and giving each of them a unique memory adress? So that I can change myMatrix without changing a, b or c. I do explicitly search for some kind of multi-assignment.

Thanks in advance!

Answer 1

use the [copy] module

>>> import copy
>>> new_matrix = copy.deepcopy(myMatrix)

Answer 2

As Burhan Khalid and juanchopanza have pointed out, what happens in your example will be different in, for example,

1. the case where "myMatrix" is actually an array of 5 values (in which case "a" will get the first value and "e" will get the last value), and
2. the case where "myMatrix" is an instance of an Object (in which case "a" through "e" will each refer to the same object).

It sounds like you're thinking of case 2, and hoping for something like a macro which will automatically expand your single assignment statement (with a single Right Hand Side Value, whether Deep Copied or not) into 5 assignment statements, each with its own Left Hand Side, Right Hand Side, and Deep Copy.

I don't know of any way to do this, and I would point out that:

• When most OO languages encounter an assignment operation like yours with an Object on the Right Hand Side, the compiler/interpreter looks for a "copy constructor" for the class of the RHS Object, and uses it (if found) to generate the value (an Object reference) which is actually assigned to the LHS. Can you even imagine what the syntax could look like for what you're describing, where the copy constructor is supposed to be called 5 times to yield 5 different Objects on the RHS, references to which are then assigned to five different variables on the LHS? What could you possibly write in a single assignment statement that would make this intent clear?

• If you're writing code where Deep vs. Shallow copies will actually have an effect on behavior then IMHO you owe it to yourself and anyone else who has to read and maintain your code to make this obvious and explicit - like the answer from wong2, repeated 5 times (once for each of the 5 variables).