PipePy to generator

This uses Python's passing values into a generator functionality. The generator must use a = (yield b) syntax. The result is another generator that yields whatever the original generator yields, while the return value of each yield is the next non-empty line of the PipePy instance.

from pipepy import echo

def upperize():
    line = yield
    while True:
        line = (yield line.upper())

# `upperize` is a function, `upperize()` is a generator
list(echo("aaa\nbbb") | upperize())
# <<< ["AAA\n", "BBB\n"]

The result is a generator, so it can be piped into another command:

print(echo("aaa\nbbb") | upperize() | grep("AAA"))
# <<< AAA