damccorm commented on code in PR #34912:
URL: https://github.com/apache/beam/pull/34912#discussion_r2330244749
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website/www/site/content/en/documentation/programming-guide.md:
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@@ -1183,6 +1183,100 @@ func init() {
> parameters to a single `emitter function`.
</span>
+{{< paragraph class="language-python">}}
Review Comment:
```suggestion
{{< paragraph class="language-python">}}
```
Nit
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website/www/site/content/en/documentation/programming-guide.md:
##########
@@ -1183,6 +1183,100 @@ func init() {
> parameters to a single `emitter function`.
</span>
+{{< paragraph class="language-python">}}
+Proper use of return vs yield in Python Functions.
+{{< /paragraph >}}
+
+<span class="language-python">
+
+> **Returning a single element (e.g., `return element`) is incorrect**
+> The `process` method in Beam must return an *iterable* of elements.
Returning a single value like an integer or string
+> (e.g., `return element`) leads to a runtime error (`TypeError: 'int' object
is not iterable`) or incorrect results since the return value
+> will be treated as an iterable. Always ensure your return type is iterable.
+
+</span>
+
+{{< highlight python >}}
+# Incorrectly Returning a single string instead of a sequence
+class ReturnIndividualElement(beam.DoFn):
+ def process(self, element):
+ return element
+
+with beam.Pipeline() as pipeline:
+ (
+ pipeline
+ | "CreateExamples" >> beam.Create(["foo"])
+ | "MapIncorrect" >> beam.ParDo(ReturnIndividualElement())
+ | "Print" >> beam.Map(print)
+ )
+ # prints:
+ # f
+ # o
+ # o
+{{< /highlight >}}
+
+<span class="language-python">
+
+> **Returning a list (e.g., `return [element1, element2]`) is valid because
List is Iterable**
+> This approach works well when emitting multiple outputs from a single call
and is easy to read for small datasets.
+
+</span>
+
+{{< highlight python >}}
+# Returning a list of strings
+class ReturnWordsFn(beam.DoFn):
+ def process(self, element):
+ # Split the sentence and return all words longer than 2 characters as
a list
+ return [word for word in element.split() if len(word) > 2]
+
+with beam.Pipeline() as pipeline:
+ (
+ pipeline
+ | "CreateSentences_Return" >> beam.Create([ # Create a collection of
sentences
+ "Apache Beam is powerful", # Sentence 1
+ "Try it now" # Sentence 2
+ ])
+ | "SplitWithReturn" >> beam.ParDo(ReturnWordsFn()) # Apply the custom
DoFn to split words
+ | "PrintWords_Return" >> beam.Map(print) # Print each List of words
+ )
+ # prints:
+ # ['Apache', 'Beam', 'powerful']
+ # ['Try', 'now']
Review Comment:
```suggestion
# Apache
# Beam
# powerful
# Try
# now
```
When you return an iterable, each element in the iterable is part of the
pcollection
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