Passing by reference or value

[CanadaGuy]

Being new to Python, I figured I was bound to run into something like this. I'm used to programming where values are passed around, and I had to go to great lengths to operate on references. Now in Python it seems to be the reverse. I wanted to make sure I'm not overlooking something in this fairly simple example:

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a = objectA b = objectB   new_list = [     a,     b,     a,     b,     a]   print(new_list)

If I execute this code, (I think) I will get a list of the addresses of each object. In Python, this would produce a result where all the 'a' objects would be at one address, and all the 'b' objects would be at another. Is it the (only) way that if I want new instances of the a and b objects, I need to use something like the following instead?

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import copy a = objectA b = objectB   new_list = [     copy.copy(a),     copy.copy(b),     copy.copy(a),     copy.copy(b),     copy.copy(a)]   print(new_list)

I learned of the idea from a few StackOverflow posts for lists, as well as the official Python docs:
https://docs.python.org/3/library/copy.html

I just want to make sure I haven't overlooked any other ways that are either easier or more straightforward.

[Gribouillis]

You could use

1	new_list = [copy.copy(x) for x in (a, b, a, b, a)]

[CanadaGuy]

You could use

1	new_list = [copy.copy(x) for x in (a, b, a, b, a)]

Thanks. That is definitely cleaner so +1 for that. Is the copy module the only way to achieve this? I noticed that lists have a .copy() method which does a shallow copy.

[Gribouillis]

Is the copy module the only way to achieve this?

In practice, there are often other ways to create new instances, it all depends on the class. I noticed in my own code that I almost never use the copy module. For example in order to copy a dict D, one usually writes new = dict(D).

[CanadaGuy]

Thanks, I'll look into those alternative methods. These are custom classes, so I suppose if I wanted something more elegant, I could code something myself. Good to know there are alternatives.