Number of Pairs of Interchangeable Rectangles LeetCode solution in Python

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class Solution:
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    def interchangeableRectangles(self, rectangles: List[List[int]]) -> int:
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        ratios = defaultdict(int)
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        for x, y in rectangles:
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            ratios[x / y] += 1
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        res = 0
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        for val in ratios.values():
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            res += val * (val - 1) // 2
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        return res