Add Pastebin solution

solutions/system_design/pastebin/pastebin.py

@@ -0,0 +1,46 @@
+# -*- coding: utf-8 -*-
+
+from mrjob.job import MRJob
+
+
+class HitCounts(MRJob):
+
+    def extract_url(self, line):
+        """Extract the generated url from the log line."""
+        pass
+
+    def extract_year_month(self, line):
+        """Return the year and month portions of the timestamp."""
+        pass
+
+    def mapper(self, _, line):
+        """Parse each log line, extract and transform relevant lines.
+
+        Emit key value pairs of the form:
+
+        (2016-01, url0), 1
+        (2016-01, url0), 1
+        (2016-01, url1), 1
+        """
+        url = self.extract_url(line)
+        period = self.extract_year_month(line)
+        yield (period, url), 1
+
+    def reducer(self, key, value):
+        """Sum values for each key.
+
+        (2016-01, url0), 2
+        (2016-01, url1), 1
+        """
+        yield key, sum(values)
+
+    def steps(self):
+        """Run the map and reduce steps."""
+        return [
+            self.mr(mapper=self.mapper,
+                    reducer=self.reducer)
+        ]
+
+
+if __name__ == '__main__':
+    HitCounts.run()