Update 2. Working with Distinct Values and Sets.md

Author: ortizfram

Introduction to MongoDB in Python/2. Working with Distinct Values and Sets.md

@@ -159,3 +159,52 @@ Possible Answers
 ```py
 db.laureates.count_documents({"firstname": Regex("^G"), "surname": Regex("^S")})
 ```
+
+## Germany, then and now
+- [x] 1. Use a regular expression object to filter for laureates with "Germany" in their "bornCountry" value.
+- [x] 2. Use a regular expression object to filter for laureates with a "bornCountry" value starting with "Germany".
+- [x] 3. Use a regular expression object to filter for laureates born in what was at the time Germany but is now another country.
+- [x] 4. Use a regular expression object to filter for laureates born in what is now Germany but at the time was another country.
+```py
+from bson.regex import Regex
+
+# Filter for laureates with "Germany" in their "bornCountry" value
+criteria = {"bornCountry": Regex("Germany")}
+print(set(db.laureates.distinct("bornCountry", criteria)))
+```
+```py
+from bson.regex import Regex
+
+# Filter for laureates with a "bornCountry" value starting with "Germany"
+criteria = {"bornCountry": Regex("^Germany")}
+print(set(db.laureates.distinct("bornCountry", criteria)))
+```
+```py
+from bson.regex import Regex
+
+# Fill in a string value to be sandwiched between the strings "^Germany " and "now"
+criteria = {"bornCountry": Regex("^" + "Germany \(" + "now")}
+print(set(db.laureates.distinct("bornCountry", criteria)))
+```
+```py
+from bson.regex import Regex
+
+#Filter for currently-Germany countries of birth. Fill in a string value to be sandwiched between the strings "now" and "$"
+criteria = {"bornCountry": Regex("now" + " Germany\)" + "$")}
+print(set(db.laureates.distinct("bornCountry", criteria)))
+```
+
+## The prized transistor
+- [x] Save a filter criteria that finds laureates with prizes.motivation values containing "transistor" as a substring. The substring can appear anywhere within the value, so no anchoring characters are needed.
+- [x] Save to first and last the field names corresponding to a laureate's first name and last name (i.e. "surname") so that we can print out the names of these laureates.
+```py
+from bson.regex import Regex
+
+# Save a filter for laureates with prize motivation values containing "transistor" as a substring
+criteria = {"prizes.motivation": Regex("transistor")}
+
+# Save the field names corresponding to a laureate's first name and last name
+first, last = 'firstname', 'surname'
+print([(laureate[first], laureate[last]) 
+    for laureate in db.laureates.find(criteria)])
+```