heidimhurst commented on a change in pull request #14869:
URL: https://github.com/apache/beam/pull/14869#discussion_r648770142
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File path: sdks/python/apache_beam/transforms/util.py
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@@ -730,14 +731,30 @@ def from_runner_api_parameter(
return Reshuffle()
+def fn_takes_side_inputs(fn):
+ try:
+ signature = get_signature(fn)
+ except TypeError:
+ # We can't tell; maybe it does.
+ return True
+
+ return (
+ len(signature.parameters) > 1 or any(
+ p.kind == p.VAR_POSITIONAL or p.kind == p.VAR_KEYWORD
+ for p in signature.parameters.values()))
+
+
@ptransform_fn
-def WithKeys(pcoll, k):
+def WithKeys(pcoll, k, *args, **kwargs):
"""PTransform that takes a PCollection, and either a constant key or a
callable, and returns a PCollection of (K, V), where each of the values in
the input PCollection has been paired with either the constant key or a key
- computed from the value.
+ computed from the value. The callable may optionally accept positional or
+ keyword arguments, which should be passed to WithKeys directly.
"""
if callable(k):
+ if fn_takes_side_inputs(k):
+ return pcoll | Map(lambda v: (k(v, *args, **kwargs), v))
Review comment:
I was too hasty to incorporate this feedback @pabloem. Since the lambda
function does not have `*args` and `**kwargs` in the function signature, there
is no need (and no way) to pass them in directly. Instead, the lambda function
defines a wrapper which feeds `*args` and `**kwargs` directly into `k`. At
least this is how I understand what's happening here - does that make sense?
Tests were passing before (and this is the fix I'm currently using in
production with my team) so I think this change was unnecessary.
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