diff --git a/.travis.yml b/.travis.yml
index 7402e6fb6e78..a3575f60e461 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -135,7 +135,7 @@ matrix:
 
 install:
   - eval `python $TRAVIS_BUILD_DIR/ci/travis/determine_tests_to_run.py`
-  - if [ $RAY_CI_TUNE_AFFECTED != "1" ] && [ $RAY_CI_RLLIB_AFFECTED != "1" ] && [ $RAY_CI_PYTHON_AFFECTED != "1" ]; then exit; fi
+  - if [ $RAY_CI_TUNE_AFFECTED != "1" ] && [ $RAY_CI_RLLIB_AFFECTED != "1" ] && [ $RAY_CI_SERVE_AFFECTED != "1" ] && [ $RAY_CI_PYTHON_AFFECTED != "1" ]; then exit; fi
 
   - ./ci/suppress_output ./ci/travis/install-bazel.sh
   - ./ci/suppress_output ./ci/travis/install-dependencies.sh
@@ -173,6 +173,9 @@ script:
   - if [ $RAY_CI_RLLIB_AFFECTED == "1" ]; then ./ci/suppress_output python python/ray/rllib/tests/test_optimizers.py; fi
   - if [ $RAY_CI_RLLIB_AFFECTED == "1" ]; then ./ci/suppress_output python python/ray/rllib/tests/test_evaluators.py; fi
 
+  # ray serve tests
+  - if [ $RAY_CI_SERVE_AFFECTED == "1" ] && [ $RAY_CI_PY3 == "1" ]; then ./ci/suppress_output python -m pytest -v --durations=5 python/ray/experimental/serve/tests; fi
+
   # ray tests
   # Python3.5+ only. Otherwise we will get `SyntaxError` regardless of how we set the tester.
   - if [ $RAY_CI_PYTHON_AFFECTED == "1" ]; then python -c 'import sys;exit(sys.version_info>=(3,5))' || python -m pytest -v --durations=5 --timeout=300 python/ray/experimental/test/async_test.py; fi
diff --git a/ci/travis/determine_tests_to_run.py b/ci/travis/determine_tests_to_run.py
index 7518a0148d72..721447fe6e3d 100644
--- a/ci/travis/determine_tests_to_run.py
+++ b/ci/travis/determine_tests_to_run.py
@@ -5,6 +5,8 @@
 
 import os
 import subprocess
+import sys
+from pprint import pformat
 
 
 def list_changed_files(commit_range):
@@ -26,24 +28,37 @@ def list_changed_files(commit_range):
     return [s.strip() for s in out.decode().splitlines() if s is not None]
 
 
+def print_and_log(s):
+    print(s)
+    sys.stderr.write(s)
+    sys.stderr.write("\n")
+
+
 if __name__ == "__main__":
 
     RAY_CI_TUNE_AFFECTED = 0
     RAY_CI_RLLIB_AFFECTED = 0
+    RAY_CI_SERVE_AFFECTED = 0
     RAY_CI_JAVA_AFFECTED = 0
     RAY_CI_PYTHON_AFFECTED = 0
     RAY_CI_LINUX_WHEELS_AFFECTED = 0
     RAY_CI_MACOS_WHEELS_AFFECTED = 0
 
+    RAY_CI_PY3 = 1 if sys.version_info >= (3, 5) else 0
+
     if os.environ["TRAVIS_EVENT_TYPE"] == "pull_request":
 
         files = list_changed_files(os.environ["TRAVIS_COMMIT_RANGE"].replace(
             "...", ".."))
 
         skip_prefix_list = [
-            "doc/", "examples/", "dev/", "docker/", "kubernetes/", "site/"
+            "doc/", "examples/", "dev/", "docker/", "kubernetes/", "site/",
+            "ci/", ".travis.yml"
         ]
 
+        sys.stderr.write("Files Changed\n")
+        sys.stderr.write(pformat(files))
+
         for changed_file in files:
             if changed_file.startswith("python/ray/tune/"):
                 RAY_CI_TUNE_AFFECTED = 1
@@ -54,6 +69,10 @@ def list_changed_files(commit_range):
                 RAY_CI_RLLIB_AFFECTED = 1
                 RAY_CI_LINUX_WHEELS_AFFECTED = 1
                 RAY_CI_MACOS_WHEELS_AFFECTED = 1
+            elif changed_file.startswith("python/ray/experimental/serve"):
+                RAY_CI_SERVE_AFFECTED = 1
+                RAY_CI_LINUX_WHEELS_AFFECTED = 1
+                RAY_CI_MACOS_WHEELS_AFFECTED = 1
             elif changed_file.startswith("python/"):
                 RAY_CI_TUNE_AFFECTED = 1
                 RAY_CI_RLLIB_AFFECTED = 1
@@ -89,11 +108,18 @@ def list_changed_files(commit_range):
         RAY_CI_LINUX_WHEELS_AFFECTED = 1
         RAY_CI_MACOS_WHEELS_AFFECTED = 1
 
-    print("export RAY_CI_TUNE_AFFECTED={}".format(RAY_CI_TUNE_AFFECTED))
-    print("export RAY_CI_RLLIB_AFFECTED={}".format(RAY_CI_RLLIB_AFFECTED))
-    print("export RAY_CI_JAVA_AFFECTED={}".format(RAY_CI_JAVA_AFFECTED))
-    print("export RAY_CI_PYTHON_AFFECTED={}".format(RAY_CI_PYTHON_AFFECTED))
-    print("export RAY_CI_LINUX_WHEELS_AFFECTED={}"
-          .format(RAY_CI_LINUX_WHEELS_AFFECTED))
-    print("export RAY_CI_MACOS_WHEELS_AFFECTED={}"
-          .format(RAY_CI_MACOS_WHEELS_AFFECTED))
+    print_and_log("export RAY_CI_PY3={}".format(RAY_CI_PY3))
+    print_and_log(
+        "export RAY_CI_TUNE_AFFECTED={}".format(RAY_CI_TUNE_AFFECTED))
+    print_and_log(
+        "export RAY_CI_RLLIB_AFFECTED={}".format(RAY_CI_RLLIB_AFFECTED))
+    print_and_log(
+        "export RAY_CI_SERVE_AFFECTED={}".format(RAY_CI_SERVE_AFFECTED))
+    print_and_log(
+        "export RAY_CI_JAVA_AFFECTED={}".format(RAY_CI_JAVA_AFFECTED))
+    print_and_log(
+        "export RAY_CI_PYTHON_AFFECTED={}".format(RAY_CI_PYTHON_AFFECTED))
+    print_and_log("export RAY_CI_LINUX_WHEELS_AFFECTED={}".format(
+        RAY_CI_LINUX_WHEELS_AFFECTED))
+    print_and_log("export RAY_CI_MACOS_WHEELS_AFFECTED={}".format(
+        RAY_CI_MACOS_WHEELS_AFFECTED))
diff --git a/ci/travis/install-dependencies.sh b/ci/travis/install-dependencies.sh
index 20ff2e64d210..8b014ea9f635 100755
--- a/ci/travis/install-dependencies.sh
+++ b/ci/travis/install-dependencies.sh
@@ -34,7 +34,8 @@ elif [[ "$PYTHON" == "3.5" ]] && [[ "$platform" == "linux" ]]; then
   bash miniconda.sh -b -p $HOME/miniconda
   export PATH="$HOME/miniconda/bin:$PATH"
   pip install -q scipy tensorflow cython==0.29.0 gym opencv-python-headless pyyaml pandas==0.24.2 requests \
-    feather-format lxml openpyxl xlrd py-spy setproctitle pytest-timeout flaky networkx tabulate psutil aiohttp
+    feather-format lxml openpyxl xlrd py-spy setproctitle pytest-timeout flaky networkx tabulate psutil aiohttp \
+    flask
 elif [[ "$PYTHON" == "2.7" ]] && [[ "$platform" == "macosx" ]]; then
   # Install miniconda.
   wget https://repo.continuum.io/miniconda/Miniconda2-4.5.4-MacOSX-x86_64.sh -O miniconda.sh -nv
@@ -48,7 +49,8 @@ elif [[ "$PYTHON" == "3.5" ]] && [[ "$platform" == "macosx" ]]; then
   bash miniconda.sh -b -p $HOME/miniconda
   export PATH="$HOME/miniconda/bin:$PATH"
   pip install -q cython==0.29.0 tensorflow gym opencv-python-headless pyyaml pandas==0.24.2 requests \
-    feather-format lxml openpyxl xlrd py-spy setproctitle pytest-timeout flaky networkx tabulate psutil aiohttp
+    feather-format lxml openpyxl xlrd py-spy setproctitle pytest-timeout flaky networkx tabulate psutil aiohttp \
+    flask
 elif [[ "$LINT" == "1" ]]; then
   sudo apt-get update
   sudo apt-get install -y build-essential curl unzip
diff --git a/python/ray/experimental/serve/README.rst b/python/ray/experimental/serve/README.rst
index b59672c46912..4857b4309d24 100644
--- a/python/ray/experimental/serve/README.rst
+++ b/python/ray/experimental/serve/README.rst
@@ -4,18 +4,6 @@ Ray Serve Module
 ``ray.experimental.serve`` is a module for publishing your actors to
 interact with outside world.
 
-Use Case
---------
-
-Serve machine learning model
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Scalable anayltics query
-~~~~~~~~~~~~~~~~~~~~~~~~
-
-Composible pipelines
-~~~~~~~~~~~~~~~~~~~~
-
 Architecture
 ------------
 
diff --git a/python/ray/experimental/serve/__init__.py b/python/ray/experimental/serve/__init__.py
index 15757a9d5f54..cf60daaddbdb 100644
--- a/python/ray/experimental/serve/__init__.py
+++ b/python/ray/experimental/serve/__init__.py
@@ -10,8 +10,8 @@
 
 import sys
 
-assert sys.version_info >= (3, ), (
-    "ray.experimental.serve is a python3 only library")
+assert sys.version_info >= (
+    3, 5), "ray.experimental.serve is a python3 only library"
 
 from ray.experimental.serve.router import (DeadlineAwareRouter,
                                            SingleQuery)  # noqa: E402
diff --git a/python/ray/experimental/serve/example_actors.py b/python/ray/experimental/serve/example_actors.py
new file mode 100644
index 000000000000..2dd12e2ea064
--- /dev/null
+++ b/python/ray/experimental/serve/example_actors.py
@@ -0,0 +1,108 @@
+"""
+This file contains example ray servable actors. These actors
+are used for testing as well as demoing purpose.
+"""
+
+from __future__ import absolute_import, division, print_function
+
+import time
+
+import numpy as np
+
+import ray
+from ray.experimental.serve import RayServeMixin, batched_input
+
+
+@ray.remote
+class VectorizedAdder(RayServeMixin):
+    """Actor that adds scaler_increment to input batch.
+
+    result = np.array(input_batch) + scaler_increment
+    """
+
+    def __init__(self, scaler_increment):
+        self.inc = scaler_increment
+
+    @batched_input
+    def __call__(self, input_batch):
+        arr = np.array(input_batch)
+        arr += self.inc
+        return arr.tolist()
+
+
+@ray.remote
+class ScalerAdder(RayServeMixin):
+    """Actor that adds a scaler_increment to a single input."""
+
+    def __init__(self, scaler_increment):
+        self.inc = scaler_increment
+
+    def __call__(self, input_scaler):
+        return input_scaler + self.inc
+
+
+@ray.remote
+class VectorDouble(RayServeMixin):
+    """Actor that doubles the batched input."""
+
+    @batched_input
+    def __call__(self, batched_vectors):
+        matrix = np.array(batched_vectors)
+        matrix *= 2
+        return [v.tolist() for v in matrix]
+
+
+@ray.remote
+class Counter(RayServeMixin):
+    """Return the query id. Used for testing router."""
+
+    def __init__(self):
+        self.counter = 0
+
+    def __call__(self, batched_input):
+        self.counter += 1
+        return self.counter
+
+
+@ray.remote
+class CustomCounter(RayServeMixin):
+    """Return the query id. Used for testing `serve_method` signature."""
+
+    serve_method = "count"
+
+    @batched_input
+    def count(self, input_batch):
+        return [1 for _ in range(len(input_batch))]
+
+
+@ray.remote
+class SleepOnFirst(RayServeMixin):
+    """Sleep on the first request, return batch size.
+
+    Used for testing the DeadlineAwareRouter.
+    """
+
+    def __init__(self, sleep_time):
+        self.nap_time = sleep_time
+
+    @batched_input
+    def __call__(self, input_batch):
+        time.sleep(self.nap_time)
+        return [len(input_batch) for _ in range(len(input_batch))]
+
+
+@ray.remote
+class SleepCounter(RayServeMixin):
+    """Sleep on input argument seconds, return the query id.
+
+    Used to test the DeadlineAwareRouter.
+    """
+
+    def __init__(self):
+        self.counter = 0
+
+    def __call__(self, inp):
+        time.sleep(inp)
+
+        self.counter += 1
+        return self.counter
diff --git a/python/ray/experimental/serve/examples/adder.py b/python/ray/experimental/serve/examples/adder.py
deleted file mode 100644
index 862e61c7150b..000000000000
--- a/python/ray/experimental/serve/examples/adder.py
+++ /dev/null
@@ -1,47 +0,0 @@
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-
-import numpy as np
-
-import ray
-from ray.experimental.serve import RayServeMixin, batched_input
-
-
-@ray.remote
-class VectorizedAdder(RayServeMixin):
-    """Actor that adds scaler_increment to input batch.
-
-    result = np.array(input_batch) + scaler_increment
-    """
-
-    def __init__(self, scaler_increment):
-        self.inc = scaler_increment
-
-    @batched_input
-    def __call__(self, input_batch):
-        arr = np.array(input_batch)
-        arr += self.inc
-        return arr.tolist()
-
-
-@ray.remote
-class ScalerAdder(RayServeMixin):
-    """Actor that adds a scaler_increment to a single input."""
-
-    def __init__(self, scaler_increment):
-        self.inc = scaler_increment
-
-    def __call__(self, input_scaler):
-        return input_scaler + self.inc
-
-
-@ray.remote
-class VectorDouble(RayServeMixin):
-    """Actor that doubles the batched input."""
-
-    @batched_input
-    def __call__(self, batched_vectors):
-        matrix = np.array(batched_vectors)
-        matrix *= 2
-        return [v.tolist() for v in matrix]
diff --git a/python/ray/experimental/serve/examples/counter.py b/python/ray/experimental/serve/examples/counter.py
deleted file mode 100644
index 369d53fb5a8e..000000000000
--- a/python/ray/experimental/serve/examples/counter.py
+++ /dev/null
@@ -1,29 +0,0 @@
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-
-import ray
-from ray.experimental.serve import RayServeMixin, batched_input
-
-
-@ray.remote
-class Counter(RayServeMixin):
-    """Return the query id. Used for testing router."""
-
-    def __init__(self):
-        self.counter = 0
-
-    def __call__(self, batched_input):
-        self.counter += 1
-        return self.counter
-
-
-@ray.remote
-class CustomCounter(RayServeMixin):
-    """Return the query id. Used for testing `serve_method` signature."""
-
-    serve_method = "count"
-
-    @batched_input
-    def count(self, input_batch):
-        return [1 for _ in range(len(input_batch))]
diff --git a/python/ray/experimental/serve/examples/halt.py b/python/ray/experimental/serve/examples/halt.py
deleted file mode 100644
index eceb94d8653e..000000000000
--- a/python/ray/experimental/serve/examples/halt.py
+++ /dev/null
@@ -1,41 +0,0 @@
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-
-import time
-
-import ray
-from ray.experimental.serve import RayServeMixin, batched_input
-
-
-@ray.remote
-class SleepOnFirst(RayServeMixin):
-    """Sleep on the first request, return batch size.
-
-    Used for testing the DeadlineAwareRouter.
-    """
-
-    def __init__(self, sleep_time):
-        self.nap_time = sleep_time
-
-    @batched_input
-    def __call__(self, input_batch):
-        time.sleep(self.nap_time)
-        return [len(input_batch) for _ in range(len(input_batch))]
-
-
-@ray.remote
-class SleepCounter(RayServeMixin):
-    """Sleep on input argument seconds, return the query id.
-
-    Used to test the DeadlineAwareRouter.
-    """
-
-    def __init__(self):
-        self.counter = 0
-
-    def __call__(self, inp):
-        time.sleep(inp)
-
-        self.counter += 1
-        return self.counter
diff --git a/python/ray/experimental/serve/frontend/http_frontend.py b/python/ray/experimental/serve/frontend/http_frontend.py
index 66973caca838..5d6c8a3a1513 100644
--- a/python/ray/experimental/serve/frontend/http_frontend.py
+++ b/python/ray/experimental/serve/frontend/http_frontend.py
@@ -4,10 +4,6 @@
 
 import time
 
-import uvicorn
-from starlette.applications import Starlette
-from starlette.responses import JSONResponse
-
 import ray
 
 
@@ -45,12 +41,15 @@ def __init__(self, ip="0.0.0.0", port=8080, router="DefaultRouter"):
         self.router = ray.experimental.named_actors.get_actor(router)
 
     def start(self):
-        default_app = Starlette()
+        # We have to import flask here to avoid Flask's
+        # "Working outside of request context." error
+        from flask import Flask, request, jsonify  # noqa: E402
+
+        default_app = Flask(__name__)
 
-        @default_app.route("/{actor}", methods=["GET", "POST"])
-        async def dispatch_remote_function(request):
-            data = await request.json()
-            actor_name = request.path_params["actor"]
+        @default_app.route("/<actor_name>", methods=["GET", "POST"])
+        def dispatch_remote_function(actor_name):
+            data = request.get_json()
 
             slo_seconds = data.pop("slo_ms") / 1000
             deadline = time.perf_counter() + slo_seconds
@@ -59,14 +58,12 @@ async def dispatch_remote_function(request):
 
             result_future = unwrap(
                 self.router.call.remote(actor_name, inp, deadline))
-
-            # TODO(simon): change to asyncio ray.get
             result = ray.get(result_future)
 
-            return JSONResponse({
+            return jsonify({
                 "success": True,
                 "actor": actor_name,
                 "result": result
             })
 
-        uvicorn.run(default_app, host=self.ip, port=self.port)
+        default_app.run(host=self.ip, port=self.port)
diff --git a/python/ray/experimental/serve/mixin.py b/python/ray/experimental/serve/mixin.py
index 858572634a04..9061d93ba13a 100644
--- a/python/ray/experimental/serve/mixin.py
+++ b/python/ray/experimental/serve/mixin.py
@@ -1,3 +1,9 @@
+"""
+Mixins are classes that are designed to be included in other class.
+This module tries to provide a RayServeMixin class that makes
+an actor servable by ray.serve
+"""
+
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
diff --git a/python/ray/experimental/serve/router/routers.py b/python/ray/experimental/serve/router/routers.py
index b11849039ce9..fa103dc0f3e1 100644
--- a/python/ray/experimental/serve/router/routers.py
+++ b/python/ray/experimental/serve/router/routers.py
@@ -92,8 +92,8 @@ def register_actor(
 
     def set_replica(self, actor_name, new_replica_count):
         """Scale a managed actor according to new_replica_count."""
-        assert actor_name in self.managed_actors, (
-            ACTOR_NOT_REGISTERED_MSG(actor_name))
+        assert actor_name in self.managed_actors, ACTOR_NOT_REGISTERED_MSG(
+            actor_name)
 
         current_replicas = len(self.actor_handles[actor_name])
 
@@ -120,8 +120,8 @@ def call(self, actor_name, data, deadline_s):
             List[ray.ObjectID] with length 1, the object ID wrapped inside is
                 the result object ID when the query is executed.
         """
-        assert actor_name in self.managed_actors, (
-            ACTOR_NOT_REGISTERED_MSG(actor_name))
+        assert actor_name in self.managed_actors, ACTOR_NOT_REGISTERED_MSG(
+            actor_name)
 
         result_object_id = get_new_oid()
 
@@ -179,8 +179,8 @@ def loop(self):
 
     def _get_next_batch(self, actor_name: str) -> List[SingleQuery]:
         """Get next batch of request for the actor whose name is provided."""
-        assert actor_name in self.query_queues, (
-            ACTOR_NOT_REGISTERED_MSG(actor_name))
+        assert actor_name in self.query_queues, ACTOR_NOT_REGISTERED_MSG(
+            actor_name)
 
         inputs = []
         batch_size = self.max_batch_size[actor_name]
diff --git a/python/ray/experimental/serve/tests/test_actors.py b/python/ray/experimental/serve/tests/test_actors.py
index 3b2748b73bf3..0f6e600302db 100644
--- a/python/ray/experimental/serve/tests/test_actors.py
+++ b/python/ray/experimental/serve/tests/test_actors.py
@@ -7,8 +7,12 @@
 
 import ray
 from ray.experimental.serve import SingleQuery
-from ray.experimental.serve.examples.adder import ScalerAdder, VectorizedAdder
-from ray.experimental.serve.examples.counter import Counter, CustomCounter
+from ray.experimental.serve.example_actors import (
+    ScalerAdder,
+    VectorizedAdder,
+    Counter,
+    CustomCounter,
+)
 from ray.experimental.serve.object_id import get_new_oid
 
 INCREMENT = 3
diff --git a/python/ray/experimental/serve/tests/test_deadline_router.py b/python/ray/experimental/serve/tests/test_deadline_router.py
index d1d4d6769794..3c0e5e5187b5 100644
--- a/python/ray/experimental/serve/tests/test_deadline_router.py
+++ b/python/ray/experimental/serve/tests/test_deadline_router.py
@@ -8,8 +8,12 @@
 import pytest
 
 import ray
-from ray.experimental.serve.examples.adder import ScalerAdder, VectorizedAdder
-from ray.experimental.serve.examples.halt import SleepCounter, SleepOnFirst
+from ray.experimental.serve.example_actors import (
+    ScalerAdder,
+    VectorizedAdder,
+    SleepCounter,
+    SleepOnFirst,
+)
 from ray.experimental.serve.object_id import unwrap
 from ray.experimental.serve.router import DeadlineAwareRouter, start_router
 
diff --git a/python/ray/experimental/serve/tests/test_default_app.py b/python/ray/experimental/serve/tests/test_default_app.py
index 5eb758c5f7ed..88ed845f230a 100644
--- a/python/ray/experimental/serve/tests/test_default_app.py
+++ b/python/ray/experimental/serve/tests/test_default_app.py
@@ -9,7 +9,7 @@
 
 import ray
 from ray.experimental.serve import DeadlineAwareRouter
-from ray.experimental.serve.examples.adder import VectorizedAdder
+from ray.experimental.serve.example_actors import VectorizedAdder
 from ray.experimental.serve.frontend import HTTPFrontendActor
 from ray.experimental.serve.router import start_router
 
@@ -17,7 +17,7 @@
 NUMBER_OF_TRIES = 5
 
 
-@pytest.fixture
+@pytest.fixture(scope="module")
 def get_router():
     # We need this many workers so resource are not oversubscribed
     ray.init(num_cpus=4)
diff --git a/python/ray/experimental/serve/utils/__init__.py b/python/ray/experimental/serve/utils/__init__.py
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/python/ray/experimental/serve/utils/priority_queue.py b/python/ray/experimental/serve/utils/priority_queue.py
index 05b7045b43a5..479b917e8ead 100644
--- a/python/ray/experimental/serve/utils/priority_queue.py
+++ b/python/ray/experimental/serve/utils/priority_queue.py
@@ -5,7 +5,23 @@
 import heapq
 
 
-class PriorityQueue:
+class BaseQueue:
+    """Abstract base class for queue abstraction"""
+
+    def push(self, item):
+        raise NotImplementedError()
+
+    def pop(self):
+        raise NotImplementedError()
+
+    def try_pop(self):
+        raise NotImplementedError()
+
+    def __len__(self):
+        raise NotImplementedError()
+
+
+class PriorityQueue(BaseQueue):
     """A min-heap class wrapping heapq module."""
 
     def __init__(self):
@@ -25,3 +41,25 @@ def try_pop(self):
 
     def __len__(self):
         return len(self.q)
+
+
+class FIFOQueue(BaseQueue):
+    """A min-heap class wrapping heapq module."""
+
+    def __init__(self):
+        self.q = []
+
+    def push(self, item):
+        self.q.append(item)
+
+    def pop(self):
+        return self.q.pop(0)
+
+    def try_pop(self):
+        if len(self.q) == 0:
+            return None
+        else:
+            return self.pop()
+
+    def __len__(self):
+        return len(self.q)