In 14 500 500 In 15 is Out 15 True In 16 500 In 17 500 In 18 is Out 18

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In [14]: a, b = 500, 500
In [15]: a is b
Out[15]: True
In [16]: a = 500
In [17]: b = 500
In [18]: a is b
Out[18]: False
In [22]: b = 200
In [23]: a = 200
In [24]: a is b
Out[24]: True