How to ignore specific elements being added to Python list

Question

I have a python list. Let's say it's an empty list. Is there any way that I can make the list ignore specifc characters that when someone tries to add, at the time of list creation itself.

Suppose I want to ignore all the '.' characters to be ignored when someone tries to append the character usinng list.append('.').

Is there any way to mention that at the time of list creation itself?

Answer 1

I don't think you should do this, but if you really have to, you could subclass a list like so:

class IgnoreList(list):
    def append(self, item, *args, **kwargs):
        if item == '.':
            return
        return super(IgnoreList, self).append(item)

But is horribly un-pythonic. A better solution is to just check the value before calling append.

if value != '.':
    my_list.append(value)

Answer 2

The best way to do this in python would be to create a new class with the desired behaviour

>>> class mylist(list):
...     def append(self, x):
...             if x != ".":
...                     super().append(x)
... 
>>> l = mylist()
>>> l.append("foo")
>>> l
['foo']
>>> l.append(".")
>>> l
['foo']