I found a bug in python set.update(set())

Python Help
1

Documentations says that set can not have mutable elements but when i am trying to add set to the set using update method it is getting executed without throwing any error.

pls confirm if i am correct else explain the reason of the same.

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2

set.update() does not “add” the passed in parameter to itself. It assumes it to be an iterable and adds all of the elements produced by the iterable to the set.

3

Do you mean this?

>>> a = {1, 2, 3, 4}
>>> b = {4, 5}
>>> a.update(b)
>>> a
{1, 2, 3, 4, 5}

What’s the problem? None of the elements of b are mutable.

4

A=set()
B=A.update(A)

Set is mutable but cannot contain mutable elements
Then why A.update() gets executed without throwing any error whereas i m trying to add a mutable element which is a set to the set

5

You are not trying to add mutable element with this:

>>> s = set('abc')
>>> s
{'a', 'b', 'c'}
>>> s.update([1, 2, 3])
>>> s
{1, 2, 'c', 3, 'b', 'a'}

If you try to add mutable item it will raise an error:

>>> s.update([{1}])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'set'
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