TheAlgorithms-Python

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"""
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wiki: https://en.wikipedia.org/wiki/Heterogram_(literature)#Isograms
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"""
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def is_isogram(string: str) -> bool:
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    """
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    An isogram is a word in which no letter is repeated.
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    Examples of isograms are uncopyrightable and ambidextrously.
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    >>> is_isogram('Uncopyrightable')
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    True
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    >>> is_isogram('allowance')
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    False
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    >>> is_isogram('copy1')
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    Traceback (most recent call last):
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     ...
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    ValueError: String must only contain alphabetic characters.
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    """
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    if not all(x.isalpha() for x in string):
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        raise ValueError("String must only contain alphabetic characters.")
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    letters = sorted(string.lower())
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    return len(letters) == len(set(letters))
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if __name__ == "__main__":
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    input_str = input("Enter a string ").strip()
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    isogram = is_isogram(input_str)
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    print(f"{input_str} is {'an' if isogram else 'not an'} isogram.")
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