#
# Copyright 2014 Quantopian, Inc.
#
# Licensed 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 abc
from sys import float_info
from six import with_metaclass
from numpy import isfinite
import zipline.utils.math_utils as zp_math
from zipline.errors import BadOrderParameters
from zipline.utils.compat import consistent_round
[docs]class ExecutionStyle(with_metaclass(abc.ABCMeta)):
"""
Abstract base class representing a modification to a standard order.
"""
_exchange = None
[docs] @abc.abstractmethod
def get_limit_price(self, is_buy):
"""
Get the limit price for this order.
Returns either None or a numerical value >= 0.
"""
raise NotImplemented
[docs] @abc.abstractmethod
def get_stop_price(self, is_buy):
"""
Get the stop price for this order.
Returns either None or a numerical value >= 0.
"""
raise NotImplemented
@property
def exchange(self):
"""
The exchange to which this order should be routed.
"""
return self._exchange
[docs]class MarketOrder(ExecutionStyle):
"""
Class encapsulating an order to be placed at the current market price.
"""
def __init__(self, exchange=None):
self._exchange = exchange
def get_limit_price(self, _is_buy):
return None
def get_stop_price(self, _is_buy):
return None
[docs]class LimitOrder(ExecutionStyle):
"""
Execution style representing an order to be executed at a price equal to or
better than a specified limit price.
"""
def __init__(self, limit_price, asset=None, exchange=None):
"""
Store the given price.
"""
check_stoplimit_prices(limit_price, 'limit')
self.limit_price = limit_price
self._exchange = exchange
self.asset = asset
def get_limit_price(self, is_buy):
return asymmetric_round_price(
self.limit_price,
is_buy,
tick_size=(0.01 if self.asset is None else self.asset.tick_size)
)
def get_stop_price(self, _is_buy):
return None
[docs]class StopOrder(ExecutionStyle):
"""
Execution style representing an order to be placed once the market price
reaches a specified stop price.
"""
def __init__(self, stop_price, asset=None, exchange=None):
"""
Store the given price.
"""
check_stoplimit_prices(stop_price, 'stop')
self.stop_price = stop_price
self._exchange = exchange
self.asset = asset
def get_limit_price(self, _is_buy):
return None
def get_stop_price(self, is_buy):
return asymmetric_round_price(
self.stop_price,
not is_buy,
tick_size=(0.01 if self.asset is None else self.asset.tick_size)
)
[docs]class StopLimitOrder(ExecutionStyle):
"""
Execution style representing a limit order to be placed with a specified
limit price once the market reaches a specified stop price.
"""
def __init__(self, limit_price, stop_price, asset=None, exchange=None):
"""
Store the given prices
"""
check_stoplimit_prices(limit_price, 'limit')
check_stoplimit_prices(stop_price, 'stop')
self.limit_price = limit_price
self.stop_price = stop_price
self._exchange = exchange
self.asset = asset
def get_limit_price(self, is_buy):
return asymmetric_round_price(
self.limit_price,
is_buy,
tick_size=(0.01 if self.asset is None else self.asset.tick_size)
)
def get_stop_price(self, is_buy):
return asymmetric_round_price(
self.stop_price,
not is_buy,
tick_size=(0.01 if self.asset is None else self.asset.tick_size)
)
def asymmetric_round_price(price, prefer_round_down, tick_size, diff=0.95):
"""
Asymmetric rounding function for adjusting prices to the specified number
of places in a way that "improves" the price. For limit prices, this means
preferring to round down on buys and preferring to round up on sells.
For stop prices, it means the reverse.
If prefer_round_down == True:
When .05 below to .95 above a specified decimal place, use it.
If prefer_round_down == False:
When .95 below to .05 above a specified decimal place, use it.
In math-speak:
If prefer_round_down: [<X-1>.0095, X.0195) -> round to X.01.
If not prefer_round_down: (<X-1>.0005, X.0105] -> round to X.01.
"""
precision = zp_math.number_of_decimal_places(tick_size)
multiplier = int(tick_size * (10 ** precision))
diff -= 0.5 # shift the difference down
diff *= (10 ** -precision) # adjust diff to precision of tick size
diff *= multiplier # adjust diff to value of tick_size
# Subtracting an epsilon from diff to enforce the open-ness of the upper
# bound on buys and the lower bound on sells. Using the actual system
# epsilon doesn't quite get there, so use a slightly less epsilon-ey value.
epsilon = float_info.epsilon * 10
diff = diff - epsilon
# relies on rounding half away from zero, unlike numpy's bankers' rounding
rounded = tick_size * consistent_round(
(price - (diff if prefer_round_down else -diff)) / tick_size
)
if zp_math.tolerant_equals(rounded, 0.0):
return 0.0
return rounded
def check_stoplimit_prices(price, label):
"""
Check to make sure the stop/limit prices are reasonable and raise
a BadOrderParameters exception if not.
"""
try:
if not isfinite(price):
raise BadOrderParameters(
msg="Attempted to place an order with a {} price "
"of {}.".format(label, price)
)
# This catches arbitrary objects
except TypeError:
raise BadOrderParameters(
msg="Attempted to place an order with a {} price "
"of {}.".format(label, type(price))
)
if price < 0:
raise BadOrderParameters(
msg="Can't place a {} order with a negative price.".format(label)
)