json.dump to a gzip file in python 3

Question

I'm trying to write a object to a gzipped json file in one step (minimising code, and possibly saving memory space). My initial idea (python3) was thus:

import gzip, json
with gzip.open("/tmp/test.gz", mode="wb") as f:
  json.dump({"a": 1}, f)

This however fails: TypeError: 'str' does not support the buffer interface, which I think has to do with a string not being encoded to bytes. So what is the proper way to do this?

Current solution that I'm unhappy with:

Opening the file in text-mode solves the problem:

import gzip, json
with gzip.open("/tmp/test.gz", mode="wt") as f:
  json.dump({"a": 1}, f)

however I don't like text-mode. In my mind (and maybe this is wrong, but supported by this), text mode is used to fix line-endings. This shouldn't be an issue because json doesn't have line endings, but I don't like it (possibly) messing with my bytes, it (possibly) is slower because it's looking for line-endings to fix, and (worst of all) I don't understand why something about line-endings fixes my encoding problems?

Answer 1

offtopic: I should have dived into the docs a bit further than I initially did.

The python docs show:

Normally, files are opened in text mode, that means, you read and write strings from and to the file, which are encoded in a specific encoding (the default being UTF-8). 'b' appended to the mode opens the file in binary mode: now the data is read and written in the form of bytes objects. This mode should be used for all files that don’t contain text.

I don't fully agree that the result from a json encode is a string (I think it should be a set of bytes, since it explicitly defines that it uses utf-8 encoding), but I noticed this before. So I guess text mode it is.