Why another task-running/subprocess-spawning Python library? As usual, the short answer is “there were already great 80-90% solutions out there, but none that fit our needs 100%.” Specifically:
Multiple tasks at once - almost no other Python command-line oriented libraries allow for invocations like:
runner --core-opts task1 --task1-opts task2 --task2-opts
and the few that do have half-baked implementations of the feature or are lacking in other ways.
Ability to mirror and capture subprocess output simultaneously (in addition to everything flowing from that, like the ability to transparently auto-respond) - the standard library’s
subprocesscan’t do this and most other tools choose one or the other, or have other tradeoffs such as not supporting (or only supporting!) pseudoterminals.
Simplicity - tools that try to do many things often suffer for it due to lack of focus. We wanted to build something clean and simple that just did one thing (ok…two things) well.
Customizability/control - Invoke was designed to work well with (and be a foundation for) other tools such as Fabric’s second version, and we felt that the work needed to adapt existing tools towards this goal would impede progress.
Some of the pre-existing solutions in this space in the Python world include:
Argh: One of the more appealing options, but being built on argparse it doesn’t support the multi-task invocation we needed. Also has its own “prior art” list which is worth your time.
Baker: Nice and simple, but unfortunately too much so for our needs.
Paver: Tries to do too much, clunky API, user-hostile error messages, multi-task feature existed but was lacking.
Argparse: The modern gold standard for CLI parsing (albeit without command execution). Unfortunately, we were unable to get multiple tasks working despite lots of experimentation. Multiple tasks with their own potentially overlapping argument names, simply doesn’t mesh with how
argparsethinks about the command line.
Click: is actually not pre-existing (Invoke’s first public releases predate Click by a number of years) but it deserves mention anyway, as it’s become popular in this particular niche.