问题描述
我正在尝试使用Python解压缩* .Z文件。我通过FTP（二进制模式）下载了它。该文件使用7zip成功解压缩（文件中的信息表示其类型为 Z）。原始文件位于。
I'm trying to uncompress a *.Z file using Python. I downloaded it via FTP (binary mode). The file successfully uncompresses with 7zip (whose "info" on the file says it's of type "Z"). The original file can be found at ftp://cddis.gsfc.nasa.gov/gps/products/1860/igr18600.sp3.Z.
我已经阅读了Python中zlib模块的用法，并使用了一些测试代码：
I've read up on the use of the zlib module in Python and have some test code I'm using:
import zlib
comp_data = open('C:\Temp\igr18600.sp3.Z', 'rb').read()
print(comp_data[0:10])
uncomp_data = zlib.decompress(comp_data)
with open('c:\temp\igr18600.sp3', 'wb') as f:
f.write(uncomp_data)
f.close()
执行此操作时，将得到以下输出：
When I execute this I get the following output:
b'\x1f\x9d\x90#\xc6@\x91\x01#F'
Traceback (most recent call last):
File "test.py", line 7, in <module>
uncomp_data = zlib.decompress(comp_data)
zlib.error: Error -3 while decompressing data: incorrect header check
zlib显然不喜欢标题。前两个字节似乎与压缩文件的正确魔术数字序列0x1F9d匹配（每个）。
zlib clearly doesn't like the header. The first couple of bytes appear to match the proper magic number sequence 0x1F9d for a compressed file (per https://en.wikipedia.org/wiki/List_of_file_signatures).
在紧要关头，我可以通过直接掏空7zip来解决此问题。但是我希望找到一个纯Python类型的答案。尽管一天中大部分时间都在搜寻答案（或此错误消息），但我的运气并不好。也许我的搜索技能正在萎缩？
In a pinch I can work around this by shelling out to 7zip directly. But I was hoping to find a pure Python type of answer. Despite spending most of the day googling for an answer (or this error message) I haven't had much luck. Perhaps my search skills are atrophying?
推荐答案
Python在模块中没有等效的Unix uncompress，这是您需要解压缩的。 Z文件。您可能需要a）外壳到Unix compress命令，b）外壳到gzip，c）外壳到7-zip（gzip和7-zip都具有解压缩.Z文件的能力），d）修改在C中原始的解压缩代码并链接到Python（该代码可在线获得），或者e）在本机Python中编写自己的LZW解压缩器。
Python does not have the equivalent of Unix uncompress available in a module, which is what you'd need to decompress a .Z file. You would either need to a) shell out to the Unix compress command, b) shell out to gzip, c) shell out to 7-zip (both gzip and 7-zip have the ability to decompress .Z files), d) modify the original uncompress code in C and link that to Python (the code is available online), or e) write your own LZW decompressor in native Python.
对于d），您可以在mathematica.stackexchange.com 上的答案中找到我编写的一些C代码来。请参见 unlzw（）函数。
For d), you can find some C code I wrote to do this job in this answer on mathematica.stackexchange.com. See the unlzw() function.
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