Previously, calling order() in initalize resulted in a weird
stack trace. It now returns a well formulated error that is
readable to the user through the API. Adding a slippage
kwarg to test_algorithm and simfactor was necessary because
slippage can only be called during init. Previously initaliazed
was never set to true and calls to init-only function were sprinkled
around the code in non-init sections. Code changes were to enforce
init-only rules.
Make the error messages for {DoBadThing}PostInit no longer reference "the
simulation", since the algorithm may not actually be running as a simulation.
Adds four new methods to the Zipline API that can be used as circuit-breakers
to interrupt the execution of an algorithm. The API methods are:
`set_max_position_size`
`set_max_order_size`
`set_max_order_count`
`set_long_only`
Internally, these methods are implemented by each registering a TradingControl
callback object with the TradingAlgorithm. During
TradingAlgorithm.__validate_order_params (and thus before any side-effects of
the order call occur), each callback's `validate` method is called with
information about the order to be placed and the algorithm's current state,
raising an exception if the callback detects that an error condition has been breached.
existing `limit_price` and `stop_price` parameters. The goal of this change is
to refactor the existing ordering API to provide a cleaner interface for
defining more complex order types.
Adds a new module, zipline.finance.execution, which defines the ExecutionStyle
abstract base class, along with concrete MarketOrder, LimitOrder, StopOrder,
and StopLimitOrder subclasses.
Adds a new `style` keyword argument to the function signature of the `order`
API method, which accepts an instance of ExecutionStyle.
The existing limit_price and stop_price parameters are still supported at this
time, but are converted into the new ExecutionStyle objects before being passed
to Blotter.order.
Raise exceptions when the slippage model returns transactions
that are non-sensical, i.e. those with zero volume, buy transactions
when the order is a sell (and vice-versa), and transactions that are
for a larger amount than the corresponding order.
TODO: After adding a unit test suite that covers just the blotter,
add tests that exercise this logic to that suite.
Delaney Granizo-Mackenzie