使用python限制bz2文件解压？

Question

I have numerous files that are compressed in the bz2 format and I am trying to uncompress them in a temporary directory using python to then analyze. There are hundreds of thousands of files so manually decompressing the files isn't feasible so I wrote the following script.

My issue is that whenever I try to do this, the maximum file size is 900 kb even though a manual decompression has each file around 6 MB. I am not sure if this is a flaw in my code and how I am saving the data as a string to then copy to the file or a problem with something else. I have tried this with different files and I know that it works for files smaller than 900 kb. Has anyone else had a similar problem and knows of a solution?

My code is below:

import numpy as np
import bz2
import os
import glob

def unzip_f(filepath):
    '''
    Input a filepath specifying a group of Himiwari .bz2 files with common names
    Outputs the path of all the temporary files that have been uncompressed

    '''


    cpath = os.getcwd() #get current path
    filenames_ = []  #list to add filenames to for future use

    for zipped_file in glob.glob(filepath):  #loop over the files that meet the name criterea
        with bz2.BZ2File(zipped_file,'rb') as zipfile:   #Read in the bz2 files
            newfilepath = cpath +'/temp/'+zipped_file[-47:-4]     #create a temporary file
            with open(newfilepath, "wb") as tmpfile: #open the temporary file
                for i,line in enumerate(zipfile.readlines()):
                    tmpfile.write(line) #write the data from the compressed file to the temporary file



            filenames_.append(newfilepath)
    return filenames_


path_='test/HS_H08_20180930_0710_B13_FLDK_R20_S*bz2'
unzip_f(path_)   

It returns the correct file paths with the wrong sizes capped at 900 kb.

Answer 1

It turns out this issue is due to the files being multi stream which does not work in python 2.7. There is more info here as mentioned by jasonharper and here . Below is a solution just using the Unix command to decompress the bz2 files and then moving them to the temporary directory I want. It is not as pretty but it works.

import numpy as np
import os
import glob
import shutil

def unzip_f(filepath):
    '''
    Input a filepath specifying a group of Himiwari .bz2 files with common names
    Outputs the path of all the temporary files that have been uncompressed

    '''


    cpath = os.getcwd() #get current path
    filenames_ = []  #list to add filenames to for future use

    for zipped_file in glob.glob(filepath):  #loop over the files that meet the name criterea
        newfilepath = cpath +'/temp/'   #create a temporary file
        newfilename = newfilepath + zipped_file[-47:-4]

        os.popen('bzip2 -kd ' + zipped_file)
        shutil.move(zipped_file[-47:-4],newfilepath)

        filenames_.append(newfilename)
    return filenames_



path_='test/HS_H08_20180930_0710_B13_FLDK_R20_S0*bz2'

unzip_f(path_)   

Answer 2

This is a known limitation in Python2, where the BZ2File class doesn't support multiple streams. This can be easily resolved by using bz2file , https://pypi.org/project/bz2file/ , which is a backport of Python3 implementation and can be used as a drop-in replacement.

After running pip install bz2file you can just replace bz2 with it: import bz2file as bz2 and everything should just work :)

The original Python bug report: https://bugs.python.org/issue1625