Function bwt_transform

data_compression/burrows_wheeler.py:54–90

:param s: The string that will be used at bwt algorithm :return: the string composed of the last char of each row of the ordered rotations and the index of the original string at ordered rotations list :raises TypeError: If the s parameter type is not str :raises ValueError: If

(s: str)

def bwt_transform(s: str) -> BWTTransformDict:
    """
    :param s: The string that will be used at bwt algorithm
    :return: the string composed of the last char of each row of the ordered
    rotations and the index of the original string at ordered rotations list
    :raises TypeError: If the s parameter type is not str
    :raises ValueError: If the s parameter is empty
    Examples:

    >>> bwt_transform("^BANANA")
    {'bwt_string': 'BNN^AAA', 'idx_original_string': 6}
    >>> bwt_transform("a_asa_da_casa")
    {'bwt_string': 'aaaadss_c__aa', 'idx_original_string': 3}
    >>> bwt_transform("panamabanana")
    {'bwt_string': 'mnpbnnaaaaaa', 'idx_original_string': 11}
    >>> bwt_transform(4)
    Traceback (most recent call last):
        ...
    TypeError: The parameter s type must be str.
    >>> bwt_transform('')
    Traceback (most recent call last):
        ...
    ValueError: The parameter s must not be empty.
    """
    if not isinstance(s, str):
        raise TypeError("The parameter s type must be str.")
    if not s:
        raise ValueError("The parameter s must not be empty.")

    rotations = all_rotations(s)
    rotations.sort()  # sort the list of rotations in alphabetically order
    # make a string composed of the last char of each rotation
    response: BWTTransformDict = {
        "bwt_string": "".join([word[-1] for word in rotations]),
        "idx_original_string": rotations.index(s),
    }
    return response


def reverse_bwt(bwt_string: str, idx_original_string: int) -> str: