Tapystry
This is a small library for handling effects, inspired by redux-saga.
Installation
pip install tapystry
Usage
It's most easily understood by example!
import tapystry as tap
def broadcaster(value):
yield tap.Broadcast('key', value)
return "success"
def incrementer():
value = 0
while True:
winner, received_val = yield tap.Race(dict(
receive=tap.Receive('key'),
exit=tap.Receive('exit'),
))
if winner == 'exit':
break
else:
assert winner == 'receive'
value += received_val
return value
def fn():
# fork off a strand that increments
recv_strand = yield tap.CallFork(incrementer)
# broadcast a value to add
success = yield tap.Call(broadcaster, (5,))
assert success == "success"
# equivalent syntax using yield from
success = yield from broadcaster(8)
assert success == "success"
# forked process is not yet done
assert not recv_strand.is_done()
yield tap.Broadcast("exit")
# this value won't get received
success = yield tap.Call(broadcaster, (1,))
assert success == "success"
value = yield tap.Join(recv_strand)
return value
assert tap.run(fn) == 13What's the point?
This lets you isolate side effects really easily.
For example, you could fork a Strand that repeatedly polls a database for events.
Then you could have a bunch of independent logic that decides what to do with that.
Everything except the logic touching the database is pure and can be unit tested easily.
