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import sys


def test_small_int_id_is_constant():
    assert id(12) == id(12)
    x = 128
    y = 128
    assert id(x) == id(y) == id(128)


def test_object_id_is_constant():
    x = object()
    xid = id(x)
    assert id(x) == xid


def test_double_id_is_constant():
    assert id(12.2) == id(12.2)
    x = 128.12
    y = 128.12
    assert id(x) == id(y) == id(128.12)


def test_id_is_constant_even_when_object_changes():
    l = []
    assert id(l) == id(l)
    lid = id(l)
    l.append(12)
    assert id(l) == lid

def test_identity():
    assert True is True
    assert memoryview(b"").readonly is True # compare a PInt bool (from C) to a boolean

    assert 12 is 12
    assert memoryview(b"123").nbytes == 3 # compare PInt (from C) to an int
    class I(int): pass
    assert I(12) is not 12
    assert 12.0 is 12.0

    nan = float('nan')
    assert nan is nan

def test_string_interned():
    x='1234'
    y='1234'
    assert id(x) == id(y) == id('1234') == id(sys.intern('1234')) == id(sys.intern(x)) == id(sys.intern(y))

# skip until is fixed: GR-28568
# def test_string_noninterned():
#     x = '1234'
#     y = x * 2
#     z = x * 2
#     assert id(y) != id(z)

