Unable to unzip a downloaded file in Google Colab

Question

I've read dozens of questions about unzipping files from Google Colab. My question is different, you will read why.

I need to unzip a zip file on Google Colab in order to perform some computation on the images in it. The problem is that all the different utilities that I've used don't recognize the zip file as a zip file.

1. To avoid any problem in the creation of the zip file, I let Google Drive create one for me, simply selecting more than one image and clicking on download. Google Drive automatically creates a zip file containing the images. Let's call it images.zip
2. I re-upload images.zip on GDrive and share it copying its link
3. Then, in Google Colab, I download locally images.zip:

import urllib
import os

drive_url = 'the_link_to_the_zip_file'
file_name = 'images.zip'

urllib.request.urlretrieve(drive_url, file_name)

os.listdir()

Obtaining: ['.config', 'images.zip', 'drive', 'sample_data'], so the file was successfully downloaded.

Now I would like to unzip it.

Using zipfile

import zipfile

zip_ref = zipfile.ZipFile("images.zip", "r")
zip_ref.extractall()
zip_ref.close()

The error that I get:

BadZipFile                                Traceback (most recent call last)

<ipython-input-41-eca398f38f4a> in <module>()
----> 1 zip_ref = zipfile.ZipFile("xyz.zip", "r")
      2 zip_ref.extractall()
      3 zip_ref.close()

1 frames

/usr/lib/python3.6/zipfile.py in __init__(self, file, mode, compression, allowZip64)
   1129         try:
   1130             if mode == 'r':
-> 1131                 self._RealGetContents()
   1132             elif mode in ('w', 'x'):
   1133                 # set the modified flag so central directory gets written

/usr/lib/python3.6/zipfile.py in _RealGetContents(self)
   1196             raise BadZipFile("File is not a zip file")
   1197         if not endrec:
-> 1198             raise BadZipFile("File is not a zip file")
   1199         if self.debug > 1:
   1200             print(endrec)

BadZipFile: File is not a zip file

Using unzip

!unzip -uq "images.zip" -d "/content/drive/My Drive/Test"

The error that I get:

End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.
unzip:  cannot find zipfile directory in one of images.zip or
        images.zip.zip, and cannot find images.zip.ZIP, period.

Obviously images.zip is a perfectly fine zip file, that I can open and modify both on my computer and online using Google Drive.

Note: I obtain the same result also uploading a zip file that I've created on my computer. Initially I was thinking that maybe my zip utility was broken, but now what it seems broken is Google Colab...

Note2: The solution isn't just access directly to the file images.zip in Drive and unzip from there because it could happen that I need to download locally a zip from someone else Drive

Many thanks

Answer 1

I think I got what the problem is. Looks like the file you are tying to extract is not a zip. Try this to verify if it is really a zipfile.

!apt install file
!file <location_of_zip_file> 

I suspect that the file you downloaded is not zipfile because you might not have provided the direct URL to the file.