[lang-ref] ( init_with_size ) ( python )

def test_init_with_size():
    # items = [x] * n

    items = ['Camera!'] * 3

    assert items == ['Camera!', 'Camera!', 'Camera!']

def test_init_with_size_alternative():
    # this is trap. 
    items = [['a', 'b']] * 3
    assert items == [['a', 'b'], ['a', 'b'], ['a', 'b']]
    assert items[0] is items[1]  # same object ...

    items[0].append('c') # so this changes all elements
    assert items == [['a', 'b', 'c'], ['a', 'b', 'c'], ['a', 'b', 'c']]

    # this is safe.
    items = [['a', 'b'] for _ in range(3)] # distinct objects
    assert items == [['a', 'b'], ['a', 'b'], ['a', 'b']]
    assert items[0] is not items[1]  # different objects

    items[0].append('c') # this changes first element only
    assert items == [['a', 'b', 'c'], ['a', 'b'], ['a', 'b']]