Update 4. Aggregation Pipelines: Let the Server Do It For You.md

Author: ortizfram

Introduction to MongoDB in Python/4. Aggregation Pipelines: Let the Server Do It For You.md

@@ -81,3 +81,19 @@ Possible Answers
 - [ ] "laureates.share", ["3"], ["3"], "laureates.share"
 - [ ] "laureates.share", {"3"}, {"3"}, "laureates.share"
 - [ ] "$laureates.share", {"3"}, {"3"}, "$laureates.share"
+## 🦍 Organizing prizes
+In the slides at the beginning of this lesson, we saw a two-stage aggregation pipeline to determine the number of prizes awarded in total. How many prizes were awarded (at least partly) to organizations?
+- [x] Fill out pipeline to determine the number of prizes awarded (at least partly) to organizations. To do this, you'll first need to $match on the "gender" that designates organizations.
+- [x] Then, use a field path to project the number of prizes for each organization as the "$size" of the "prizes" array. Recall that to specify the value of a field "<my_field>", you use the field path "$<my_field>".
+- [x] Finally, use a single group {"_id": None} to sum over the values of all organizations' prize counts.
+```py
+# Count prizes awarded (at least partly) to organizations as a sum over sizes of "prizes" arrays.
+pipeline = [
+    {"$match": {"gender": "org"}},
+    {"$project": {"n_prizes": {"$size": "$prizes"}}},
+    {"$group": {"_id": None, "n_prizes_total": {"$sum": "$n_prizes"}}}
+]
+
+print(list(db.laureates.aggregate(pipeline)))
+```
+      [{'_id': None, 'n_prizes_total': 27}]