Max Difference You Can Get From Changing an Integer LeetCode solution in Python

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class Solution:
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    def maxDiff(self, num: int) -> int:
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        num = str(num)
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        i = next((i for i in range(len(num)) if num[i] != "9"), -1)  # first non-9 digit
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        hi = int(num.replace(num[i], "9"))
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        if num[0] != "1":
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            lo = int(num.replace(num[0], "1"))
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        else:
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            i = next((i for i in range(len(num)) if num[i] not in "01"), -1)
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            lo = int(num.replace(num[i], "0") if i > 0 else num)
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        return hi - lo