2016-06-02 9:17 GMT+02:00 Antoine Pitrou solipsis@pitrou.net:

Yeah, Python 2.7 includes are JSON parser and JSON is human readble (but not really designed to be modified by a human).

I had a technical issue: I wanted to produce JSON output and keep nice human output at the same time. I found a nice trick: by default write human output to stdout, but write JSON to stdout and human output to stderr in JSON mode.

At the end, you get a simple CLI:

$ python3 -m perf.timeit --json 1+1 > run.json ......................... Average: 18.3 ns +- 0.3 ns (25 runs x 3 samples x 10^7 loops)

$ python3 -m perf < run.json

Average: 18.3 ns +- 0.3 ns (25 runs x 3 samples x 10^7 loops)

The JSON can contain metadata as well:

$ python3 -m perf.timeit --metadata --json 1+1 > run.json Metadata:

• aslr: enabled
• cpu_count: 4
• (...) ......................... Average: 18.2 ns +- 0.0 ns (25 runs x 3 samples x 10^7 loops)

$ python3 -m perf < run.json Metadata:

• aslr: enabled
• cpu_count: 4
• (...) Average: 18.2 ns +- 0.0 ns (25 runs x 3 samples x 10^7 loops)

There are two kinds of objects: a single run, or a result composed of multiple runs. The format is one JSON object per line.

Example of single runs using individual JSON files and then combine them:

$ python3 -m perf.timeit --raw --json 1+1 > run1.json warmup 1: 18.3 ns sample 1: 18.3 ns sample 2: 18.3 ns sample 3: 18.3 ns

$ python3 -m perf.timeit --raw --json 1+1 > run2.json warmup 1: 18.2 ns sample 1: 18.2 ns sample 2: 18.2 ns sample 3: 18.2 ns

$ python3 -m perf.timeit --raw --json 1+1 > run3.json warmup 1: 18.2 ns sample 1: 18.2 ns sample 2: 18.2 ns sample 3: 18.2 ns

$ python3 -m perf < run1.json # single run Average: 18.3 ns +- 0.0 ns (3 samples x 10^7 loops)

$ cat run1.json run2.json run3.json | python3 -m perf # 3 runs

Average: 18.2 ns +- 0.0 ns (3 runs x 3 samples x 10^7 loops)

Victor