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

@@ -214,3 +214,19 @@ Possible Answers
 Instructions
 - [x] In your aggregation pipeline pipeline, use the "gender" field to limit results to people (that is, not organizations).
 - [x] Count prizes for which the laureate's "bornCountry" is not also the "country" of any of their affiliations for the prize. Be sure to use field paths (precede a field name with "$") when appropriate.
+```py
+pipeline = [
+    # Limit results to people; project needed fields; unwind prizes
+    {"$match": {"gender": {"$ne": "org"}}},
+    {"$project": {"bornCountry": 1, "prizes.affiliations.country": 1}},
+    {"$unwind": "$prizes"},
+  
+    # Count prizes with no country-of-birth affiliation
+    {"$addFields": {"bornCountryInAffiliations": {"$in": ["$bornCountry", "$prizes.affiliations.country"]}}},
+    {"$match": {"bornCountryInAffiliations": False}},
+    {"$count": "awardedElsewhere"},
+]
+
+print(list(db.laureates.aggregate(pipeline)))
+```
+      [{'awardedElsewhere': 478}]