Added sample for using Cloud Spanner with App Engine Python 3.7 runtime. (#1757)

* Added sample for using Cloud Spanner with App Engine Python 3.7 runtime.

* Minor fixes.

* Minor fixes.

Author: chenyumic

appengine/standard_python37/spanner/app.yaml

@@ -0,0 +1,5 @@
+runtime: python37
+
+env_variables:
+  SPANNER_INSTANCE: "YOUR-SPANNER-INSTANCE-ID"
+  SPANNER_DATABASE: "YOUR-SPANNER-DATABASE-ID"

appengine/standard_python37/spanner/main.py

@@ -0,0 +1,35 @@
+# Copyright 2018 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# [START gae_python37_cloudsql_mysql]
+import os
+
+from flask import Flask
+from google.cloud import spanner
+
+app = Flask(__name__)
+spanner_client = spanner.Client()
+
+instance_id = os.environ.get('SPANNER_INSTANCE')
+database_id = os.environ.get('SPANNER_DATABASE')
+
+
+@app.route('/')
+def main():
+    database = spanner_client.instance(instance_id).database(database_id)
+    with database.snapshot() as snapshot:
+        cursor = snapshot.execute_sql('SELECT 1')
+    results = list(cursor)
+
+    return 'Query Result: {}'.format(results[0][0])

appengine/standard_python37/spanner/main_test.py

@@ -0,0 +1,26 @@
+# Copyright 2018 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+def test_main():
+    import main
+
+    main.database_id = 'example-db'
+
+    main.app.testing = True
+    client = main.app.test_client()
+
+    r = client.get('/')
+    assert r.status_code == 200
+    assert 'Query Result: 1' in r.data.decode('utf-8')

appengine/standard_python37/spanner/requirements.txt

@@ -0,0 +1,2 @@
+google-cloud-spanner==1.6.0
+Flask==1.0.2