<type>documentation</type>
<domain>intro</domain>
<id>tutorial-debugging-launch</id>
<title>Tutorial: Execution Environment</title>
<date>$Date: 2013-06-27 19:22:37 -0400 (Thu, 27 Jun 2013) $</date>
<product>per+</product>

In this tutorial we've been running code in the default environment and with the default
Python interpreter. In a real project you may want to specify one or more of the
following:

* Python interpreter and version
* PYTHONPATH
* Environment variables
* Initial run directory
* Options sent to Python
* Command line arguments

Wing lets you set these for your project as a whole and for specific files.

**Project Properties**

The ``Environment`` and ``Debug/Execute`` tabs in the `Project Properties
<script:view-project-properties>`__ dialog, accessed from the ``Project`` menu, can be
used to select the Python interpreter that is being used, the effective ``PYTHONPATH``,
the values of environment variables, the initial directory for the debug process, and any
options passed to Python itself.

In most cases, ``Project Properties`` is where you will make changes to the runtime
environment for all the project code that you execute and debug.

Try this out now by adding an environment variable ``TESTPROJECT=1`` to ``Environment`` in
``Project Properties``. Then restart debugging and look at ``os.environ`` in the ``Debug
Probe`` to confirm that the new environment variable is defined.

**File Properties and Launch Configurations**

``File Properties`` are used to configure the command line arguments sent to a file when
it is executed or debugged, and optionally to override the project-defined environment
on a file by file basis.

The ``File Properties`` dialog is accessed from the ``Current File Properties`` item in
the ``Source`` menu or by right-clicking on a file in the editor or ``Project`` tool and
selecting ``Properties``.

.. image:: file-properties.png
  :width: 504
  :height: 254

The most common use of ``File Properties`` is simply to set the command line arguments to
use with the file. Try this now by bringing up ``File Properties`` for ``example1.py`` and
set the run arguments in the ``Debug/Execute`` tab to ``test args``.

Now if you restart debugging and type the following in the ``Debug Console`` you will see
that the environment and arguments have been set::

  os.environ.get('TESTPROJECT')
  sys.argv[1:]
  
The output should be::

  1
  ['test', 'args']

To also override the project-defined environment for a particular file, define a ``Launch
Configuration`` and select it in ``File Properties``. This sets up an environment like
that which can be specified in ``Project Properties`` and pairs it with a particular set
of command line arguments.  A launch configuration can be reused with multiple files
or in ``Named Entry Points`` (see below).

Try this now by bringing up ``File Properties`` for ``example1.py`` again and selecting
``Use Selected Launch Configuration`` for ``Environment`` under the ``Debug/Execute`` tab.
Press the ``New`` button that appears, use``My Launch Config`` as the name for the new
launch configuration, and press ``OK``. Wing will show the properties dialog for the new
launch configuration.

Next enter run arguments ``other args`` and change the ``Environment`` to ``Add to Project
Values`` and enter ``TESTFILE=2`` and ``TESTPROJECT=``. This adds environment variable
``TESTFILE`` and removes the ``TESTPROJECT`` from the inherited project-defined
environment.

Now restart debugging again and enter this in the ``Debug Console``::

  os.environ.get('TESTPROJECT')
  os.environ.get('TESTFILE')
  sys.argv[1:]

The output should be::

  None
  2
  ['other', 'args']

See `File Properties <ref:proj/file-properties>`__ and `Launch Configurations
<ref:proj/launch-configs>`__ for details.

**Main Entry Point**

You can specify one file in your project as the main entry point for debugging and
execution. When this
is set, debugging will always start there unless you use ``Debug Current File`` in the
``Debug`` menu.

To set a main entry point use ``Set Current as Main Entry Point`` in the ``Debug`` menu,
right click on the ``Project`` tool and select ``Set as Main Entry Point``, or use the
``Main Entry Point`` property under the ``Debug`` tab of the ``Project Properties`` dialog.

Try this now by setting ``example1.py`` as the main entry point. After doing so, it is no
longer necessary to bring ``example1.py`` to front in order to start debugging it.

Whether or not you set a main entry point depends on the nature of your project.

See `Specifying Main Entry Points <ref:debug/main-entry-point>`__ for details.

**Named Entry Points**

In some projects it is more convenient to define multiple entry points for executing and
debugging code. To accomplish this, ``Named Entry Points`` can be set up from the
``Debug`` menu. Each named entry point binds an environment, either specified in the
project or in a launch configuration, to a particular file. Once defined, they can be
assigned a key binding or accessed from the ``Debug Named Entry Point`` and ``Execute
Named Entry Point`` items in the ``Debug`` menu.

Named Entry Points are a good way to launch a single file with different arguments or
environment.

See `Named Entry Points <ref:debug/named-entry-points>`__ for details.
