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https://issues.apache.org/jira/browse/AIRFLOW-850?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16727516#comment-16727516
 ] 

ASF GitHub Bot commented on AIRFLOW-850:
----------------------------------------

kaxil closed pull request #4349: [AIRFLOW-850] Add a PythonSensor
URL: https://github.com/apache/incubator-airflow/pull/4349
 
 
   

This is a PR merged from a forked repository.
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diff --git a/airflow/contrib/sensors/python_sensor.py 
b/airflow/contrib/sensors/python_sensor.py
new file mode 100644
index 0000000000..68bc7497ea
--- /dev/null
+++ b/airflow/contrib/sensors/python_sensor.py
@@ -0,0 +1,81 @@
+# -*- coding: utf-8 -*-
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+
+from airflow.sensors.base_sensor_operator import BaseSensorOperator
+from airflow.utils.decorators import apply_defaults
+
+
+class PythonSensor(BaseSensorOperator):
+    """
+    Waits for a Python callable to return True.
+
+    User could put input argument in templates_dict
+        e.g templates_dict = {'start_ds': 1970}
+    and access the argument by calling `kwargs['templates_dict']['start_ds']`
+    in the the callable
+
+    :param python_callable: A reference to an object that is callable
+    :type python_callable: python callable
+    :param op_kwargs: a dictionary of keyword arguments that will get unpacked
+        in your function
+    :type op_kwargs: dict
+    :param op_args: a list of positional arguments that will get unpacked when
+        calling your callable
+    :type op_args: list
+    :param provide_context: if set to true, Airflow will pass a set of
+        keyword arguments that can be used in your function. This set of
+        kwargs correspond exactly to what you can use in your jinja
+        templates. For this to work, you need to define `**kwargs` in your
+        function header.
+    :type provide_context: bool
+    :param templates_dict: a dictionary where the values are templates that
+        will get templated by the Airflow engine sometime between
+        ``__init__`` and ``execute`` takes place and are made available
+        in your callable's context after the template has been applied.
+    :type templates_dict: dict of str
+    """
+
+    template_fields = ('templates_dict',)
+    template_ext = tuple()
+
+    @apply_defaults
+    def __init__(
+            self,
+            python_callable,
+            op_args=None,
+            op_kwargs=None,
+            provide_context=False,
+            templates_dict=None,
+            *args, **kwargs):
+        super(PythonSensor, self).__init__(*args, **kwargs)
+        self.python_callable = python_callable
+        self.op_args = op_args or []
+        self.op_kwargs = op_kwargs or {}
+        self.provide_context = provide_context
+        self.templates_dict = templates_dict
+
+    def poke(self, context):
+        if self.provide_context:
+            context.update(self.op_kwargs)
+            context['templates_dict'] = self.templates_dict
+            self.op_kwargs = context
+
+        self.log.info("Poking callable: " + str(self.python_callable))
+        return_value = self.python_callable(*self.op_args, **self.op_kwargs)
+        return bool(return_value)
diff --git a/docs/code.rst b/docs/code.rst
index 61414ecbd6..e890adffec 100644
--- a/docs/code.rst
+++ b/docs/code.rst
@@ -256,6 +256,7 @@ Sensors
 .. autoclass:: 
airflow.contrib.sensors.imap_attachment_sensor.ImapAttachmentSensor
 .. autoclass:: airflow.contrib.sensors.jira_sensor.JiraSensor
 .. autoclass:: airflow.contrib.sensors.pubsub_sensor.PubSubPullSensor
+.. autoclass:: airflow.contrib.sensors.python_sensor.PythonSensor
 .. autoclass:: airflow.contrib.sensors.qubole_sensor.QuboleSensor
 .. autoclass:: airflow.contrib.sensors.redis_key_sensor.RedisKeySensor
 .. autoclass:: 
airflow.contrib.sensors.sagemaker_base_sensor.SageMakerBaseSensor
diff --git a/tests/contrib/sensors/test_python_sensor.py 
b/tests/contrib/sensors/test_python_sensor.py
new file mode 100644
index 0000000000..6c852e748a
--- /dev/null
+++ b/tests/contrib/sensors/test_python_sensor.py
@@ -0,0 +1,72 @@
+# -*- coding: utf-8 -*-
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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 unittest
+
+from airflow import DAG, configuration
+from airflow.contrib.sensors.python_sensor import PythonSensor
+from airflow.exceptions import AirflowSensorTimeout
+from airflow.models import DagBag
+from airflow.utils.timezone import datetime
+
+
+DEFAULT_DATE = datetime(2015, 1, 1)
+TEST_DAG_ID = 'python_sensor_dag'
+DEV_NULL = '/dev/null'
+
+
+class PythonSensorTests(unittest.TestCase):
+
+    def setUp(self):
+        configuration.load_test_config()
+        self.dagbag = DagBag(
+            dag_folder=DEV_NULL,
+            include_examples=True
+        )
+        self.args = {
+            'owner': 'airflow',
+            'start_date': DEFAULT_DATE
+        }
+        dag = DAG(TEST_DAG_ID, default_args=self.args)
+        self.dag = dag
+
+    def test_python_sensor_true(self):
+        t = PythonSensor(
+            task_id='python_sensor_check_true',
+            python_callable=lambda: True,
+            dag=self.dag)
+        t.run(start_date=DEFAULT_DATE, end_date=DEFAULT_DATE, 
ignore_ti_state=True)
+
+    def test_python_sensor_false(self):
+        t = PythonSensor(
+            task_id='python_sensor_check_false',
+            timeout=1,
+            python_callable=lambda: False,
+            dag=self.dag)
+        with self.assertRaises(AirflowSensorTimeout):
+            t.run(start_date=DEFAULT_DATE, end_date=DEFAULT_DATE, 
ignore_ti_state=True)
+
+    def test_python_sensor_raise(self):
+        t = PythonSensor(
+            task_id='python_sensor_check_raise',
+            python_callable=lambda: 1 / 0,
+            dag=self.dag)
+        with self.assertRaises(ZeroDivisionError):
+            t.run(start_date=DEFAULT_DATE, end_date=DEFAULT_DATE, 
ignore_ti_state=True)


 

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> Airflow should support a general purpose PythonSensor
> -----------------------------------------------------
>
>                 Key: AIRFLOW-850
>                 URL: https://issues.apache.org/jira/browse/AIRFLOW-850
>             Project: Apache Airflow
>          Issue Type: Improvement
>          Components: operators
>    Affects Versions: 1.8.0
>            Reporter: Daniel Gies
>            Assignee: Daniel Gies
>            Priority: Major
>
> Today I found myself trying to use a sensor to postpone execution until data 
> for the current execution date appeared in a file.  It occurred to me that 
> having a general purpose PythonSensor would allow developers to use the 
> sensor paradigm with arbitrary code.
> We should add a PythonSensor to the core sensors module which takes a 
> python_callable and optional args like the PythonOperator does.



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