如何在 Zipfile.open 进程中转储 json？

Question

I am trying to write a json inside a ZipFile BytesIO process. It goes like this:

import io
from zipfile import ZipFile
import json

in_memory_zip = io.BytesIO()
with ZipFile(in_memory_zip, 'w') as zipfile:
    with zipfile.open("1/1.json", 'w') as json_file:
        data = {'key': 1}
        json.dump(data, json_file, ensure_ascii=False, indent=4)

It is later saved in a Django File field. However it does not dump the data into the json_file . Finds it hard since it does not report an error message.

Answer 1

Your code 'shadows' zipfile , which won't be a problem by itself, but would cause problems if you needed zipfile later in your code. In general, don't shadow standard library identifiers and Python keywords.

Why it's a problem, I don't know, but it appears json.dump expects something from the file pointer that the file-like object that ZipFile.open() gets you doesn't have.

This is how to get around that:

import io
from zipfile import ZipFile
import json

in_memory_zip = io.BytesIO()
with ZipFile(in_memory_zip, 'w') as zf:
    with zf.open("1/1.json", 'w') as json_file:
        data = {'key': 1}
        data_bytes = json.dumps(data, ensure_ascii=False, indent=4).encode('utf-8')
        json_file.write(data_bytes)

Answer 2

The reason original code fails is that ZipFile expects binary data as input, while json.dump expects a file-like object that accepts "text" data ( str , not bytes ). You may think of the object that zf.open() returns as if it is a file that's open with "wb" mode.

So the right thing to do here is to wrap the file-like object to present text-oriented output to json.dump . And, as any text is has to be encoded to become bytes, you have to grab the solution from encodings library.

So, this works:

import io
from zipfile import ZipFile
import json
import encodings

in_memory_zip = io.BytesIO()
with ZipFile(in_memory_zip, 'w') as zipfile:
    with zipfile.open("1/1.json", 'w') as json_file:
        data = {'key': 1}
        json_writer = encodings.utf_8.StreamWriter(json_file)
        # JSON spec literally fixes interchange encoding as UTF-8: https://datatracker.ietf.org/doc/html/rfc8259#section-8.1
        json.dump(data, json_writer, ensure_ascii=False, indent=4)