According to the Python docs:

class zipfile.ZipFile(file[, mode[, compression[, allowZip64]]])  Open a ZIP file, where file can be either a path to a file (a string) or a file-like object. 

So, to open the file in memory, just create a file-like object (perhaps using BytesIO).

file_like_object = io.BytesIO(my_zip_data)zipfile_ob = zipfile.ZipFile(file_like_object)

PYTHON 3

import ioimport zipfilezip_buffer = io.BytesIO()with zipfile.ZipFile(zip_buffer, "a", zipfile.ZIP_DEFLATED, False) as zip_file:    for file_name, data in [('1.txt', io.BytesIO(b'111')), ('2.txt', io.BytesIO(b'222'))]:        zip_file.writestr(file_name, data.getvalue())with open('C:/1.zip', 'wb') as f:    f.write(zip_buffer.getvalue())

From the article In-Memory Zip in Python:

Below is a post of mine from May of 2008 on zipping in memory with Python, re-posted since Posterous is shutting down.

I recently noticed that there is a for-pay component available to zip files in-memory with Python. Considering this is something that should be free, I threw together the following code. It has only gone through very basic testing, so if anyone finds any errors, let me know and I’ll update this.

import zipfileimport StringIOclass InMemoryZip(object):    def __init__(self):        # Create the in-memory file-like object        self.in_memory_zip = StringIO.StringIO()    def append(self, filename_in_zip, file_contents):        '''Appends a file with name filename_in_zip and contents of         file_contents to the in-memory zip.'''        # Get a handle to the in-memory zip in append mode        zf = zipfile.ZipFile(self.in_memory_zip, "a", zipfile.ZIP_DEFLATED, False)        # Write the file to the in-memory zip        zf.writestr(filename_in_zip, file_contents)        # Mark the files as having been created on Windows so that        # Unix permissions are not inferred as 0000        for zfile in zf.filelist:            zfile.create_system = 0                return self    def read(self):        '''Returns a string with the contents of the in-memory zip.'''        self.in_memory_zip.seek(0)        return self.in_memory_zip.read()    def writetofile(self, filename):        '''Writes the in-memory zip to a file.'''        f = file(filename, "w")        f.write(self.read())        f.close()if __name__ == "__main__":    # Run a test    imz = InMemoryZip()    imz.append("test.txt", "Another test").append("test2.txt", "Still another")    imz.writetofile("test.zip")