Min Stack LeetCode solution in Python

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# Runtime: 117 ms (Top 35.13%) | Memory: 18.5 MB (Top 10.03%)
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class MinStack:
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    def __init__(self):
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        self.stack = []
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    def push(self, val: int) -> None:
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        if not self.stack:
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            self.stack.append((val, val))
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        else:
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            self.stack.append((val, min(val, self.stack[-1][1])))
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    def pop(self) -> None:
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        if self.stack:
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            self.stack.pop()
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    def top(self) -> int:
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        if self.stack:
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            return self.stack[-1][0]
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        else:
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            return None
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    def getMin(self) -> int:
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        if self.stack:
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            return self.stack[-1][1]
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        else:
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            return None