python中的基本lzw压缩帮助

Question

我只是想编写一个非常基本的脚本,它将获取一些输入文本并用lzw压缩它,使用这个包:http://packages.python.org/lzw/

我以前从来没有尝试过使用python进行任何编码而且完全混淆了=( - 我也找不到任何关于它的文档,除了包信息.

这就是我所拥有的:

import lzw

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

任何形式的任何帮助或指针将不胜感激!

谢谢=)

Answer 1

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

你可以阅读的伪代码的压缩和解压 这里

还有什么你感到困惑的吗？

这是一个例子:

蟒蛇

在此版本中,dicts包含混合类型数据:

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:此示例取自此处