[nousermane]

python3 is (relatively) slow to startup, and this is something that got significantly worse with 2->3 migration:

  $ time python3 -c ''
  real    0m0.029s

  $ time python2 -c ''
  real    0m0.010s

  $ time bash -c ''
  real    0m0.001s

Which means - you probably don't want to have python scripts on a busy webserver, being called from classic cgi-bin (do people still use those?), or run it as -exec argument to a "find" iterating over many thousands files. Maybe a couple more of such examples. For most use-cases though, that's still fast enough.