Use Pylint to lint gRPC Python examples

Author: lidizheng

.pylintrc-examples

@@ -0,0 +1,100 @@
+[MASTER]
+ignore=
+	src/python/grpcio/grpc/beta,
+	src/python/grpcio/grpc/framework,
+	src/python/grpcio/grpc/framework/common,
+	src/python/grpcio/grpc/framework/foundation,
+	src/python/grpcio/grpc/framework/interfaces,
+
+[VARIABLES]
+
+# TODO(https://github.com/PyCQA/pylint/issues/1345): How does the inspection
+# not include "unused_" and "ignored_" by default?
+dummy-variables-rgx=^ignored_|^unused_
+
+[DESIGN]
+
+# NOTE(nathaniel): Not particularly attached to this value; it just seems to
+# be what works for us at the moment (excepting the dead-code-walking Beta
+# API).
+max-args=6
+
+[MISCELLANEOUS]
+
+# NOTE(nathaniel): We are big fans of "TODO(<issue link>): " and
+# "NOTE(<username or issue link>): ". We do not allow "TODO:",
+# "TODO(<username>):", "FIXME:", or anything else.
+notes=FIXME,XXX
+
+[MESSAGES CONTROL]
+
+disable=
+	# -- START OF EXAMPLE-SPECIFIC SUPPRESSIONS --
+	no-self-use,
+	unused-argument,
+	unused-variable,
+	# -- END OF EXAMPLE-SPECIFIC SUPPRESSIONS --
+
+	# TODO(https://github.com/PyCQA/pylint/issues/59#issuecomment-283774279):
+	# Enable cyclic-import after a 1.7-or-later pylint release that
+	# recognizes our disable=cyclic-import suppressions.
+	cyclic-import,
+	# TODO(https://github.com/grpc/grpc/issues/8622): Enable this after the
+	# Beta API is removed.
+	duplicate-code,
+	# TODO(https://github.com/grpc/grpc/issues/261): Doesn't seem to
+	# understand enum and concurrent.futures; look into this later with the
+	# latest pylint version.
+	import-error,
+	# TODO(https://github.com/grpc/grpc/issues/261): Enable this one.
+	# Should take a little configuration but not much.
+	invalid-name,
+	# TODO(https://github.com/grpc/grpc/issues/261): This doesn't seem to
+	# work for now? Try with a later pylint?
+	locally-disabled,
+	# NOTE(nathaniel): What even is this? *Enabling* an inspection results
+	# in a warning? How does that encourage more analysis and coverage?
+	locally-enabled,
+	# NOTE(nathaniel): We don't write doc strings for most private code
+	# elements.
+	missing-docstring,
+	# NOTE(nathaniel): In numeric comparisons it is better to have the
+	# lesser (or lesser-or-equal-to) quantity on the left when the
+	# expression is true than it is to worry about which is an identifier
+	# and which a literal value.
+	misplaced-comparison-constant,
+	# NOTE(nathaniel): Our completely abstract interface classes don't have
+	# constructors.
+	no-init,
+	# TODO(https://github.com/grpc/grpc/issues/261): Doesn't yet play
+	# nicely with some of our code being implemented in Cython. Maybe in a
+	# later version?
+	no-name-in-module,
+	# TODO(https://github.com/grpc/grpc/issues/261): Suppress these where
+	# the odd shape of the authentication portion of the API forces them on
+	# us and enable everywhere else.
+	protected-access,
+	# NOTE(nathaniel): Pylint and I will probably never agree on this.
+	too-few-public-methods,
+	# NOTE(nathaniel): Pylint and I wil probably never agree on this for
+	# private classes. For public classes maybe?
+	too-many-instance-attributes,
+	# NOTE(nathaniel): Some of our modules have a lot of lines... of
+	# specification and documentation. Maybe if this were
+	# lines-of-code-based we would use it.
+	too-many-lines,
+	# TODO(https://github.com/grpc/grpc/issues/261): Maybe we could have
+	# this one if we extracted just a few more helper functions...
+	too-many-nested-blocks,
+	# TODO(https://github.com/grpc/grpc/issues/261): Disable unnecessary
+	# super-init requirement for abstract class implementations for now.
+	super-init-not-called,
+	# NOTE(nathaniel): A single statement that always returns program
+	# control is better than two statements the first of which sometimes
+	# returns program control and the second of which always returns
+	# program control. Probably generally, but definitely in the cases of
+	# if:/else: and for:/else:.
+	useless-else-on-loop,
+	no-else-return,
+	# NOTE(lidiz): Python 3 make object inheritance default, but not PY2
+	useless-object-inheritance,

examples/python/helloworld/greeter_client_with_options.py

@@ -11,7 +11,7 @@
 # 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.
-"""The Python implementation of the GRPC helloworld.Greeter client with channel options and call timeout parameters."""
+"""gRPC Python helloworld.Greeter client with channel options and call timeout parameters."""
 
 from __future__ import print_function
 import logging

tools/distrib/pylint_code.sh

@@ -48,4 +48,10 @@ for dir in "${TEST_DIRS[@]}"; do
   $PYTHON -m pylint --rcfile=.pylintrc-tests -rn "$dir" || EXIT=1
 done
 
+find examples/python \
+  -iname "*.py" \
+  -not -name "*_pb2.py" \
+  -not -name "*_pb2_grpc.py" \
+  | xargs $PYTHON -m pylint --rcfile=.pylintrc-examples -rn
+
 exit $EXIT