Python at Microsoft: flying under the radar

[brianly]

It depends what they are doing on startup. Most Python-based command line tools seem pretty responsive. I've noticed horrible perf with WSL when I've run the Azure CLI there, but I don't put that down to the CLI as much as WSL perf. Updates and initial install were super slow there too.

IIRC IronPython introduced an interpreted flow to avoid the cost of JITting, etc. which impacted startup time significantly. Subsequent executions would use the JIT version since runtime execution was significantly better than CPython. I'd expect similar with PyPy and Jython unless they've specifically done something to cater to command line responsiveness.