docs(samples): Adding pagination sample. (#78)

Author: m-strzelczyk

compute/compute/snippets/quickstart.py

@@ -73,9 +73,14 @@ def list_all_instances(
         iterable collections of Instance objects as values.
     """
     instance_client = compute_v1.InstancesClient()
-    agg_list = instance_client.aggregated_list(project=project_id)
+    # Use the `max_results` parameter to limit the number of results that the API returns per response page.
+    request = compute_v1.AggregatedListInstancesRequest(project=project_id, max_results=5)
+    agg_list = instance_client.aggregated_list(request=request)
     all_instances = {}
     print("Instances found:")
+    # Despite using the `max_results` parameter, you don't need to handle the pagination
+    # yourself. The returned `AggregatedListPager` object handles pagination
+    # automatically, returning separated pages as you iterate over the results.
     for zone, response in agg_list:
         if response.instances:
             all_instances[zone] = response.instances

compute/compute/snippets/sample_pagination.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python
+
+# Copyright 2021 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 compute_images_list_page ]
+# [START compute_images_list ]
+import google.cloud.compute_v1 as compute_v1
+# [END compute_images_list ]
+# [END compute_images_list_page ]
+
+
+# [START compute_images_list ]
+def print_images_list(project: str) -> None:
+    """
+    Prints a list of all non-deprecated image names available in given project.
+
+    Args:
+        project: project ID or project number of the Cloud project you want to list images from.
+
+    Returns:
+        None.
+    """
+    images_client = compute_v1.ImagesClient()
+    # Listing only non-deprecated images to reduce the size of the reply.
+    images_list_request = compute_v1.ListImagesRequest(project=project, max_results=3,
+                                                       filter="deprecated.state != DEPRECATED")
+
+    # Although the `max_results` parameter is specified in the request, the iterable returned
+    # by the `list()` method hides the pagination mechanic. The library makes multiple
+    # requests to the API for you, so you can simply iterate over all the images.
+    for img in images_client.list(request=images_list_request):
+        print(f" -  {img.name}")
+# [END compute_images_list ]
+
+
+# [START compute_images_list_page ]
+def print_images_list_by_page(project: str, page_size: int = 10) -> None:
+    """
+    Prints a list of all non-deprecated image names available in a given project,
+    divided into pages as returned by the Compute Engine API.
+
+    Args:
+        project: project ID or project number of the Cloud project you want to list images from.
+        page_size: size of the pages you want the API to return on each call.
+
+    Returns:
+        None.
+    """
+    images_client = compute_v1.ImagesClient()
+    # Listing only non-deprecated images to reduce the size of the reply.
+    images_list_request = compute_v1.ListImagesRequest(project=project, max_results=page_size,
+                                                       filter="deprecated.state != DEPRECATED")
+
+    # Use the `pages` attribute of returned iterable to have more granular control of
+    # iteration over paginated results from the API. Each time you want to access the
+    # next page, the library retrieves that page from the API.
+    for page_num, page in enumerate(images_client.list(request=images_list_request).pages, start=1):
+        print(f"Page {page_num}: ")
+        for img in page.items:
+            print(f" - {img.name}")
+# [END compute_images_list_page ]
+
+
+if __name__ == '__main__':
+    print("=================== Flat list of images ===================")
+    print_images_list('windows-sql-cloud')
+    print("================= Paginated list of images ================")
+    print_images_list_by_page('windows-sql-cloud', 5)

compute/compute/snippets/test_sample_pagination.py

@@ -0,0 +1,30 @@
+# Copyright 2021 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.
+import typing
+
+from sample_pagination import print_images_list, print_images_list_by_page
+
+PROJECT = 'windows-sql-cloud'
+
+
+def test_pagination(capsys: typing.Any) -> None:
+    print_images_list(PROJECT)
+    out, _ = capsys.readouterr()
+    assert(len(out.splitlines()) > 2)
+
+
+def test_pagination_page(capsys: typing.Any) -> None:
+    print_images_list_by_page(PROJECT, 2)
+    out, _ = capsys.readouterr()
+    assert("Page 2" in out)