Letter Combinations of a Phone Number LeetCode solution in Python

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class Solution:
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    def letterCombinations(self, digits: str) -> List[str]:
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        mapping = {
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            "2": "abc",
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            "3": "def",
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            "4": "ghi",
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            "5": "jkl",
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            "6": "mno",
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            "7": "pqrs",
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            "8": "tuv",
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            "9": "wxyz",
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        }
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        ans = []
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        first = True
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        for i in range(len(digits)):
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            # mult: times we should print each digit
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            mult = 1
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            for j in range(i + 1, len(digits)):
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                mult *= len(mapping[digits[j]])
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            # cycles: times we should run same filling cycle
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            if not first:
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                cycles = len(ans) // mult
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            else:
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                cycles = 1
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            if times > 1:
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                cycles //= len(mapping[digits[i]])
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            # cyclically adding each digits to answer
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            answer_ind = 0
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            for _ in range(cycles):
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                for char in mapping[digits[i]]:
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                    for __ in range(mult):
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                        if first:
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                            ans.append(char)
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                        else:
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                            ans[answer_ind] += char
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                        answer_ind += 1
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            if first:
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                first = False
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        return ans