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catalyst/zipline/finance/performance/position.py
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Python

#
# 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.
"""
Position Tracking
=================
+-----------------+----------------------------------------------------+
| key | value |
+=================+====================================================+
| sid | the identifier for the security held in this |
| | position. |
+-----------------+----------------------------------------------------+
| amount | whole number of shares in the position |
+-----------------+----------------------------------------------------+
| last_sale_price | price at last sale of the security on the exchange |
+-----------------+----------------------------------------------------+
| cost_basis | the volume weighted average price paid per share |
+-----------------+----------------------------------------------------+
"""
from __future__ import division
import logbook
import math
from collections import Counter
log = logbook.Logger('Performance')
class Position(object):
def __init__(self, sid, amount=0, cost_basis=0.0,
last_sale_price=0.0, last_sale_date=None,
dividends=None):
self.sid = sid
self.amount = amount
self.cost_basis = cost_basis # per share
self.last_sale_price = last_sale_price
self.last_sale_date = last_sale_date
self.dividends = dividends or []
def update_dividends(self, midnight_utc):
"""
midnight_utc is the 0 hour for the current (not yet open) trading day.
This method will be invoked at the end of the market
close handling, before the next market open.
"""
cash_payment = 0.0
stock_payment = Counter() # maps sid to number of shares paid
unpaid_dividends = []
for dividend in self.dividends:
if midnight_utc == dividend.ex_date:
# if we own shares at midnight of the div_ex date
# we are entitled to the dividend.
dividend.amount_on_ex_date = self.amount
# stock dividend
if dividend.payment_sid:
# e.g., 33.333
raw_share_count = self.amount * float(dividend.ratio)
# e.g., 33
dividend.stock_payment = math.floor(raw_share_count)
else:
dividend.stock_payment = None
# cash dividend
if dividend.net_amount:
dividend.cash_payment = self.amount * dividend.net_amount
elif dividend.gross_amount:
dividend.cash_payment = self.amount * dividend.gross_amount
else:
dividend.cash_payment = None
if midnight_utc == dividend.pay_date:
# if it is the payment date, include this
# dividend's actual payment (calculated on
# ex_date)
if dividend.stock_payment:
stock_payment[dividend.payment_sid] += \
dividend.stock_payment
if dividend.cash_payment:
cash_payment += dividend.cash_payment
else:
unpaid_dividends.append(dividend)
self.dividends = unpaid_dividends
return cash_payment, stock_payment
def add_dividend(self, dividend):
self.dividends.append(dividend)
# Update the position by the split ratio, and return the
# resulting fractional share that will be converted into cash.
# Returns the unused cash.
def handle_split(self, split):
if self.sid != split.sid:
raise Exception("updating split with the wrong sid!")
ratio = split.ratio
log.info("handling split for sid = " + str(split.sid) +
", ratio = " + str(split.ratio))
log.info("before split: " + str(self))
# adjust the # of shares by the ratio
# (if we had 100 shares, and the ratio is 3,
# we now have 33 shares)
# (old_share_count / ratio = new_share_count)
# (old_price * ratio = new_price)
# e.g., 33.333
raw_share_count = self.amount / float(ratio)
# e.g., 33
full_share_count = math.floor(raw_share_count)
# e.g., 0.333
fractional_share_count = raw_share_count - full_share_count
# adjust the cost basis to the nearest cent, e.g., 60.0
new_cost_basis = round(self.cost_basis * ratio, 2)
# adjust the last sale price
new_last_sale_price = round(self.last_sale_price * ratio, 2)
self.cost_basis = new_cost_basis
self.last_sale_price = new_last_sale_price
self.amount = full_share_count
return_cash = round(float(fractional_share_count * new_cost_basis), 2)
log.info("after split: " + str(self))
log.info("returning cash: " + str(return_cash))
# return the leftover cash, which will be converted into cash
# (rounded to the nearest cent)
return return_cash
def update(self, txn):
if self.sid != txn.sid:
raise Exception('updating position with txn for a '
'different sid')
total_shares = self.amount + txn.amount
if total_shares == 0:
self.cost_basis = 0.0
else:
prev_direction = math.copysign(1, self.amount)
txn_direction = math.copysign(1, txn.amount)
if prev_direction != txn_direction:
# we're covering a short or closing a position
if abs(txn.amount) > abs(self.amount):
# we've closed the position and gone short
# or covered the short position and gone long
self.cost_basis = txn.price
else:
prev_cost = self.cost_basis * self.amount
txn_cost = txn.amount * txn.price
total_cost = prev_cost + txn_cost
self.cost_basis = total_cost / total_shares
self.amount = total_shares
def adjust_commission_cost_basis(self, commission):
"""
A note about cost-basis in zipline: all positions are considered
to share a cost basis, even if they were executed in different
transactions with different commission costs, different prices, etc.
Due to limitations about how zipline handles positions, zipline will
currently spread an externally-delivered commission charge across
all shares in a position.
"""
if commission.sid != self.sid:
raise Exception('Updating a commission for a different sid?')
if commission.cost == 0.0:
return
# If we no longer hold this position, there is no cost basis to
# adjust.
if self.amount == 0:
return
prev_cost = self.cost_basis * self.amount
new_cost = prev_cost + commission.cost
self.cost_basis = new_cost / self.amount
def __repr__(self):
template = "sid: {sid}, amount: {amount}, cost_basis: {cost_basis}, \
last_sale_price: {last_sale_price}"
return template.format(
sid=self.sid,
amount=self.amount,
cost_basis=self.cost_basis,
last_sale_price=self.last_sale_price
)
def to_dict(self):
"""
Creates a dictionary representing the state of this position.
Returns a dict object of the form:
"""
return {
'sid': self.sid,
'amount': self.amount,
'cost_basis': self.cost_basis,
'last_sale_price': self.last_sale_price
}
class positiondict(dict):
def __missing__(self, key):
pos = Position(key)
self[key] = pos
return pos