SimPy
=====

SimPy is a process-based discrete-event simulation framework based on standard
Python. Its event dispatcher is based on Python’s `generators`__ and can also
be used for asynchronous networking or to implement multi-agent systems (with
both, simulated and real communication).

Processes in SimPy are simple Python generator functions and are used to model
active components like customers, vehicles or agents. SimPy also provides
various types of shared *resources* to model limited capacity congestion points
(like servers, checkout counters and tunnels). From version 3.1, it will also
provide monitoring capabilities to aid in gathering statistics about resources
and processes.

Simulations can be performed “as fast as possible”, in real time (wall clock
time) or by manually stepping through the events.

Though it is theoretically possible to do continuous simulations with SimPy, it
has no features that help you with that. On the other hand, SimPy is overkill
for simulations with a fixed step size where your processes don’t interact with
each other or with shared resources — use a simple ``while`` loop in this case.

The SimPy distribution contains tutorials, in-depth documentation, and a large
number of examples.

SimPy is released under the MIT License. Simulation model developers are
encouraged to share their SimPy modeling techniques with the SimPy community.
Please post a message to the `SimPy-Users mailing list`__.

__ http://docs.python.org/3/glossary.html#term-generator
__ http://lists.sourceforge.net/lists/listinfo/simpy-users


A Simple Example
----------------

One of SimPy's main goals is to be easy to use. Here is an example for a simple
SimPy simulation: a *clock* process that prints the current simulation time at
each step::

    >>> import simpy
    >>>
    >>> def clock(env, name, tick):
    ...     while True:
    ...         print(name, env.now)
    ...         yield env.timeout(tick)
    ...
    >>> env = simpy.Environment()
    >>> env.process(clock(env, 'fast', 0.5))
    <Process(clock) object at 0x...>
    >>> env.process(clock(env, 'slow', 1))
    <Process(clock) object at 0x...>
    >>> env.run(until=2)
    fast 0
    slow 0
    fast 0.5
    slow 1
    fast 1.0
    fast 1.5

Installation
------------

SimPy requires Python 2.7, 3.2, PyPy 2.0 or above.

You can install SimPy easily via `pip <http://pypi.python.org/pypi/pip>`_::

    $ pip install -U simpy

You can also download and install SimPy manually::

    $ cd where/you/put/simpy/
    $ python setup.py install

To run SimPy’s test suite on your installation, execute::

    $ python -c "import simpy; simpy.test()"

Of course, you can keep working with SimPy 2::

    $ pip install "simpy>=2.3,<3"


Getting started
---------------

If you’ve never used SimPy before, the `SimPy tutorial`__ is a good starting
point for you. You can also try out some of the `Examples`__ shipped with
SimPy.

__ https://simpy.readthedocs.org/en/latest/simpy_intro/index.html
__ https://simpy.readthedocs.org/en/latest/examples/index.html


Documentation and Help
----------------------

You can find `a tutorial`__, `examples`__, `topical guides`__ and an `API
reference`__, as well as some information about `SimPy and its history`__ in
our `online documentation`__. For more help, contact the `SimPy-Users mailing
list`__. SimPy users are pretty helpful. You can, of course, also dig through
the `source code`__.

If you find any bugs, please post them on our `issue tracker`__.

__ https://simpy.readthedocs.org/en/latest/simpy_intro/index.html
__ https://simpy.readthedocs.org/en/latest/examples/index.html
__ https://simpy.readthedocs.org/en/latest/topical_guides/index.html
__ https://simpy.readthedocs.org/en/latest/api_reference/index.html
__ https://simpy.readthedocs.org/en/latest/about/index.html
__ https://simpy.readthedocs.org/
__ mailto:simpy-users@lists.sourceforge.net
__ https://bitbucket.org/simpy/simpy/src
__ https://bitbucket.org/simpy/simpy/issues?status=new&status=open

Enjoy simulation programming in SimPy!
