Split a zip-file into chunks with Python

Question

I have a piece of a code which creates a zip file successfully, but I need to split this file if the size of it is more that 1MB.

I have this code but it doesn't work:

    from split_file_reader.split_file_writer import SplitFileWriter
    import zipfile

    # make element tree
    tree = etree.ElementTree(batch_element)

    # make xml file and write it in stream
    xml_object = BytesIO()
    tree.write(xml_object, pretty_print=True, xml_declaration=False, encoding="utf-8")
    xml_file = xml_object.getvalue()

    final = BytesIO()

    with SplitFileWriter(final, 1_000_000) as sfw:
        with zipfile.ZipFile(sfw, "a") as zip_file:
            zip_file.writestr('Batch.xml', xml_file)

I want to retrieve the split file as bytes. The zipping part is working, but the splitting doesn't.

Answer 1

According to the split_file_reader docs, the first argument of SplitFileWriter can be a generator that produces file-like objects. That will allow you to split the zip-file into a list of BytesIO chunks.

Here is a working example script:

import zipfile
from io import BytesIO
from lxml import etree
from split_file_reader.split_file_writer import SplitFileWriter

# make element tree
# tree = etree.ElementTree(batch_element)
tree = etree.parse('/tmp/test.xml')

# make xml file and write it in stream
xml_object = BytesIO()
tree.write(xml_object, pretty_print=True, xml_declaration=False, encoding="utf-8")
xml_file = xml_object.getvalue()

chunks = []

def gen(lst):
    while True:
        lst.append(BytesIO())
        yield lst[-1]

with SplitFileWriter(gen(chunks), 1_000_000) as sfw:
    with zipfile.ZipFile(sfw, "w") as zip_file:
        zip_file.writestr('Batch.xml', xml_file)

for i, chunk in enumerate(chunks):
    print(f'chunk {i}: {len(chunk.getvalue())}')

Output:

chunk 0: 1000000
chunk 1: 1000000
chunk 2: 1000000
chunk 3: 1000000
chunk 4: 1000000
chunk 5: 887260