adding preptask sample

Python/Batch/README.md

@@ -49,6 +49,11 @@ path invocation. This sample can be run on Windows with an appropriate openssl
 binary and modified openssl invocations (i.e., `openssl.exe` instead of
 `openssl`).
 
+#### [sample4\_preparationtask.py](./sample4_preparationtask.py)
+This sample demonstrates using a `JobPreparationTask` to list environment 
+variables. This sample is geared towards Windows with the deployment of
+a Windows pool.
+
 ## Azure Batch on Linux Best Practices
 
 Although some of the Python samples are not specific to Linux, the Azure Batch

Python/Batch/sample4_preparationtask.cfg

@@ -0,0 +1,4 @@
+[DEFAULT]
+shoulddeletejob=true
+poolvmsize=small
+poolvmcount=1

Python/Batch/sample4_preparationtask.py

@@ -0,0 +1,126 @@
+# Sample4_preparationtask.py Code sample
+
+from __future__ import print_function
+try:
+    import configparser
+except ImportError:
+    import ConfigParser as configparser
+import datetime
+import os
+
+import azure.batch.batch_service_client as batch
+import azure.batch.batch_auth as batchauth
+import azure.batch.models as batchmodels
+
+import common.helpers
+
+prep_task_command = 'cmd /c set'
+
+
+def submit_job_and_add_task(batch_client, job_id, vm_size, vm_count):
+    """Submits a job to the Azure Batch service
+    and adds a simple task with preparation task
+    :param batch_client: The batch client to use.
+    :type batch_client: `batchserviceclient.BatchServiceClient`
+    :param str job_id: The id of the job to create.
+    """
+
+    pool_info = batchmodels.PoolInformation(
+        auto_pool_specification=batchmodels.AutoPoolSpecification(
+            auto_pool_id_prefix="Helloworld_jobprep",
+            pool=batchmodels.PoolSpecification(
+                vm_size=vm_size,
+                target_dedicated_nodes=vm_count,
+                cloud_service_configuration={'os_family': "4"}),
+            keep_alive=False,
+            pool_lifetime_option=batchmodels.PoolLifetimeOption.job))
+
+    job = batchmodels.JobAddParameter(
+        id=job_id,
+        pool_info=pool_info,
+        job_preparation_task=batch.models.JobPreparationTask(
+            command_line=prep_task_command,
+            wait_for_success=True)
+    )
+
+    batch_client.job.add(job)
+
+    task = batchmodels.TaskAddParameter(
+        id="HelloWorld_Task",
+        command_line=common.helpers.wrap_commands_in_shell(
+            'windows', ['echo Hello world from the Batch Hello world sample!'])
+    )
+
+    batch_client.task.add(job_id=job.id, task=task)
+
+
+def execute_sample(global_config, sample_config):
+    """Executes the sample with the specified configurations.
+
+    :param global_config: The global configuration to use.
+    :type global_config: `configparser.ConfigParser`
+    :param sample_config: The sample specific configuration to use.
+    :type sample_config: `configparser.ConfigParser`
+    """
+    # Set up the configuration
+    batch_account_key = global_config.get('Batch', 'batchaccountkey')
+    batch_account_name = global_config.get('Batch', 'batchaccountname')
+    batch_service_url = global_config.get('Batch', 'batchserviceurl')
+
+    should_delete_job = sample_config.getboolean(
+        'DEFAULT',
+        'shoulddeletejob')
+    pool_vm_size = sample_config.get(
+        'DEFAULT',
+        'poolvmsize')
+    pool_vm_count = sample_config.getint(
+        'DEFAULT',
+        'poolvmcount')
+
+    # Print the settings we are running with
+    common.helpers.print_configuration(global_config)
+    common.helpers.print_configuration(sample_config)
+
+    credentials = batchauth.SharedKeyCredentials(
+        batch_account_name,
+        batch_account_key)
+
+    batch_client = batch.BatchServiceClient(
+        credentials,
+        base_url=batch_service_url)
+
+    # Retry 5 times -- default is 3
+    batch_client.config.retry_policy.retries = 5
+    job_id = common.helpers.generate_unique_resource_name("samplePrepJob")
+
+    try:
+        submit_job_and_add_task(
+            batch_client,
+            job_id,
+            pool_vm_size,
+            pool_vm_count)
+
+        common.helpers.wait_for_tasks_to_complete(
+            batch_client,
+            job_id,
+            datetime.timedelta(minutes=25))
+
+        tasks = batch_client.task.list(job_id)
+        task_ids = [task.id for task in tasks]
+
+        common.helpers.print_task_output(batch_client, job_id, task_ids)
+    finally:
+        if should_delete_job:
+            print("Deleting job: ", job_id)
+            batch_client.job.delete(job_id)
+
+
+if __name__ == '__main__':
+    global_config = configparser.ConfigParser()
+    global_config.read(common.helpers._SAMPLES_CONFIG_FILE_NAME)
+
+    sample_config = configparser.ConfigParser()
+    sample_config.read(
+        os.path.splitext(os.path.basename(__file__))[0] + '.cfg')
+
+    execute_sample(global_config, sample_config)