batch.py

import os

env = Environment(ENV=os.environ)

def action_func(target = None, source = None, env = None):
    print('my targets', target)
    return 0

my_batched_action = env.Action(action_func, batch_key=True)

env.Command(target='hello', source='world', action=my_batched_action)
env.Command(target='goodbye', source='world', action=my_batched_action)

# The above output:
# action_func(["hello", "goodbye"], ["world", "world"])
# ('my targets', [<SCons.Node.FS.File object at 0x55e4f8737250>, <SCons.Node.FS.File object at 0x55e4f87379f0>])

my_second_batched_action = env.Action(action_func, batch_key=True)

env.Command(target='end', source='world', action=[my_batched_action, my_second_batched_action])
env.Command(target='sad', source='world', action=[my_batched_action, my_second_batched_action])

# action_func(["end"], ["world"])
# ('my targets', [<SCons.Node.FS.File object at 0x55e4f8738cb0>])
# action_func(["end"], ["world"])
# ('my targets', [<SCons.Node.FS.File object at 0x55e4f8738cb0>])
# action_func(["sad"], ["world"])
# ('my targets', [<SCons.Node.FS.File object at 0x55e4f8739250>])
# action_func(["sad"], ["world"])
# ('my targets', [<SCons.Node.FS.File object at 0x55e4f8739250>])

# I would expect it to match the first example.