feat: Add serverless scope sample (GoogleCloudPlatform#2463)

* feat: Add serverless scope sample, 142060621

* style: linter issues

* fix: lint nits

* fix: correct test values for the functions scope demo

* fix type of test

* fix return

* Update main.py

Author: grant

functions/tips/main.py

@@ -39,6 +39,8 @@
 
 # [END functions_tips_connection_pooling]
 
+from functools import reduce
+
 
 # Placeholder
 def file_wide_computation():
@@ -50,6 +52,42 @@ def function_specific_computation():
     return 1
 
 
+def light_computation():
+    numbers = list(range(1, 10))
+    return reduce(lambda x, t: t + x, numbers)
+
+
+def heavy_computation():
+    # Multiplication is more computationally expensive than addition
+    numbers = list(range(1, 10))
+    return reduce(lambda x, t: t * x, numbers)
+
+
+# [START functions_tips_global_scope]
+# [START run_tips_global_scope]
+# Global (instance-wide) scope
+# This computation runs at instance cold-start
+instance_var = heavy_computation()
+
+
+def scope_demo(request):
+    """
+    HTTP Cloud Function that declares a variable.
+    Args:
+        request (flask.Request): The request object.
+        <http://flask.pocoo.org/docs/1.0/api/#flask.Request>
+    Returns:
+        The response text, or any set of values that can be turned into a
+        Response object using `make_response`
+        <http://flask.pocoo.org/docs/1.0/api/#flask.Flask.make_response>.
+    """
+    function_var = light_computation()
+    return 'Per instance: {}, per function: {}'.format(
+        instance_var, function_var)
+# [END run_tips_global_scope]
+# [END functions_tips_global_scope]
+
+
 # [START functions_tips_lazy_globals]
 # Always initialized (at cold-start)
 non_lazy_global = file_wide_computation()

functions/tips/main_test.py

@@ -35,6 +35,12 @@ def test_lazy_globals(app):
         main.lazy_globals(flask.request)
 
 
+def test_scope_demo(app):
+    with app.test_request_context():
+        res = main.scope_demo(flask.request)
+        assert res == 'Per instance: 362880, per function: 45'
+
+
 @responses.activate
 def test_connection_pooling_200(app):
     responses.add(responses.GET, 'http://example.com',