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# Copyright 2014-2020 by Christopher C. Little. |
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# This file is part of Abydos. |
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# |
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# Abydos is free software: you can redistribute it and/or modify |
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# it under the terms of the GNU General Public License as published by |
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# the Free Software Foundation, either version 3 of the License, or |
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# (at your option) any later version. |
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# |
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# Abydos is distributed in the hope that it will be useful, |
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# but WITHOUT ANY WARRANTY; without even the implied warranty of |
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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# GNU General Public License for more details. |
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# |
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# You should have received a copy of the GNU General Public License |
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# along with Abydos. If not, see <http://www.gnu.org/licenses/>. |
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"""abydos.compression._rle. |
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Run-Length Encoding encoder/decoder |
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""" |
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from itertools import groupby |
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__all__ = ['RLE'] |
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class RLE(object): |
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"""Run-Length Encoding. |
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Cf. :cite:`Robinson:1967`. |
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Based on http://rosettacode.org/wiki/Run-length_encoding#Python |
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:cite:`rosettacode:2018`. This is licensed GFDL 1.2. |
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Digits 0-9 cannot be in text. |
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.. versionadded:: 0.3.6 |
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""" |
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def encode(self, text): |
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r"""Perform encoding of run-length-encoding (RLE). |
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Parameters |
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---------- |
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text : str |
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A text string to encode |
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Returns |
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------- |
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str |
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Word decoded by RLE |
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Examples |
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-------- |
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>>> from abydos.compression import BWT |
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>>> rle = RLE() |
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>>> bwt = BWT() |
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>>> rle.encode(bwt.encode('align')) |
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'n\x00ilag' |
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>>> rle.encode('align') |
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'align' |
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>>> rle.encode(bwt.encode('banana')) |
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'annb\x00aa' |
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>>> rle.encode('banana') |
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'banana' |
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>>> rle.encode(bwt.encode('aaabaabababa')) |
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'ab\x00abbab5a' |
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>>> rle.encode('aaabaabababa') |
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'3abaabababa' |
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.. versionadded:: 0.1.0 |
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.. versionchanged:: 0.3.6 |
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Encapsulated in class |
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""" |
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if text: |
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text = ((len(list(g)), k) for k, g in groupby(text)) |
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text = ( |
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(str(n) + k if n > 2 else (k if n == 1 else 2 * k)) |
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for n, k in text |
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) |
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return ''.join(text) |
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def decode(self, text): |
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r"""Perform decoding of run-length-encoding (RLE). |
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Parameters |
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---------- |
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text : str |
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A text string to decode |
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Returns |
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------- |
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str |
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Word decoded by RLE |
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Examples |
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-------- |
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>>> from abydos.compression import BWT |
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>>> rle = RLE() |
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>>> bwt = BWT() |
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>>> bwt.decode(rle.decode('n\x00ilag')) |
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'align' |
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>>> rle.decode('align') |
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'align' |
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>>> bwt.decode(rle.decode('annb\x00aa')) |
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'banana' |
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>>> rle.decode('banana') |
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'banana' |
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>>> bwt.decode(rle.decode('ab\x00abbab5a')) |
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'aaabaabababa' |
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>>> rle.decode('3abaabababa') |
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'aaabaabababa' |
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.. versionadded:: 0.1.0 |
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.. versionchanged:: 0.3.6 |
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Encapsulated in class |
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""" |
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mult = '' |
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decoded = [] |
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for letter in list(text): |
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if not letter.isdigit(): |
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if mult: |
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decoded.append(int(mult) * letter) |
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mult = '' |
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else: |
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decoded.append(letter) |
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else: |
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mult += letter |
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text = ''.join(decoded) |
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return text |
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if __name__ == '__main__': |
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import doctest |
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doctest.testmod() |
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chrislit /
abydos
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