python - python中的基本lzw压缩帮助

Question

我只是想写一个非常基本的脚本，它将接受一些输入文本并使用 lzw 压缩它，使用这个包：http ://packages.python.org/lzw/

我以前从未尝试过使用 python 进行任何编码，并且非常困惑 =( - 除了包信息之外，我也找不到任何关于它的在线文档。

这是我所拥有的：

import lzw

file = lzw.readbytes("collectemailinfo.txt", buffersize=1024)
enc = lzw.compress(file)
print enc

任何帮助或任何类型的指针将不胜感激！

谢谢 =)

Answer 1

这是包 API：http ://packages.python.org/lzw/lzw-module.html

您可以在此处阅读压缩和解压缩 的伪代码

你还有什么困惑的吗？

这是一个例子：

Python

在这个版本中，dicts 包含混合类型的数据：

def compress(uncompressed):
    """Compress a string to a list of output symbols."""

    # Build the dictionary.
    dict_size = 256
    dictionary = dict((chr(i), chr(i)) for i in xrange(dict_size))
    # in Python 3: dictionary = {chr(i): chr(i) for i in range(dict_size)}

    w = ""
    result = []
    for c in uncompressed:
        wc = w + c
        if wc in dictionary:
            w = wc
        else:
            result.append(dictionary[w])
            # Add wc to the dictionary.
            dictionary[wc] = dict_size
            dict_size += 1
            w = c

    # Output the code for w.
    if w:
        result.append(dictionary[w])
    return result



def decompress(compressed):
    """Decompress a list of output ks to a string."""

    # Build the dictionary.
    dict_size = 256
    dictionary = dict((chr(i), chr(i)) for i in xrange(dict_size))
    # in Python 3: dictionary = {chr(i): chr(i) for i in range(dict_size)}

    w = result = compressed.pop(0)
    for k in compressed:
        if k in dictionary:
            entry = dictionary[k]
        elif k == dict_size:
            entry = w + w[0]
        else:
            raise ValueError('Bad compressed k: %s' % k)
        result += entry

        # Add w+entry[0] to the dictionary.
        dictionary[dict_size] = w + entry[0]
        dict_size += 1

        w = entry
    return result

如何使用：

compressed = compress('TOBEORNOTTOBEORTOBEORNOT')
print (compressed)
decompressed = decompress(compressed)
print (decompressed)

输出：

['T', 'O', 'B', 'E', 'O', 'R', 'N', 'O', 'T', 256, 258, 260, 265, 259, 261, 263]
TOBEORNOTTOBEORTOBEORNOT

注意：这个例子取自这里