How to make a class field [list] read-only in python?

Question

i have self.some_field = [] in my class
Im enquiring is there a way to make this list read-only like a property?

Answer 1

You need to make it, indeed, a property...: eg, in __init__

self._some_field = []

and then later in the class's body:

@property
def some_field(self):
    return self._some_field

Note that this does not make the list itself immutable: what will fail is an assignment like, say,

self.some_field = 'bah'

not the call of a mutator, like, say,

self.some_field.append('blah')

If you want to make the field immutable, it cannot be a list, by definition (since a list is a mutable sequence) -- it must be some other type of sequence (an immutable one) which you need to define for the purpose.

Answer 2

If you mean the attribute, then make it a read-only property. If you mean the list itself, then use a tuple instead since they're immutable.