Excel Sheet Column Title LeetCode solution in Python

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class Solution:
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    def convertToTitle(self, num: int) -> str:
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        # We make this lookup list, having A-Z in ascending order
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        alpha = [
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            chr(x) for x in range(ord("A"), ord("Z") + 1)
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        ]  # range(65, 90+1) -> 91-65 = 26
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        res = ""
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        while num > 0:
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            res += alpha[
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                (num - 1) % 26
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            ]  # since 0 indexed list, num-1 % 26 gives the index of ch in alpha
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            num = (num - 1) // 26
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        return res[::-1]