From e5b4c1175ebd91f30f983ee3f253f0e9a79ce8ee Mon Sep 17 00:00:00 2001
From: Colin Delahunty <72827203+colin99d@users.noreply.github.com>
Date: Sat, 16 Oct 2021 06:42:49 -0400
Subject: [PATCH] Parity Dividends (#812)

* Refactored code, added parity

* Got call price

* Finalized feature

* added documentation

* Added changes except number limit

* Added limit to number of data points

* Updated duplicated variable names

* Added docstrings, updated filtering

* Added PV of dividends

Co-authored-by: Colin Delahunty <colindelahunty@Colins-MacBook-Air.local>
Co-authored-by: Colin Delahunty <colindelahunty@Colins-Air.indiana.edu>
---
 gamestonk_terminal/options/yfinance_model.py | 18 ++++++++++
 gamestonk_terminal/options/yfinance_view.py  | 37 +++++++++++++++++---
 2 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/gamestonk_terminal/options/yfinance_model.py b/gamestonk_terminal/options/yfinance_model.py
index 098325ddc05..4e64dd21b4b 100644
--- a/gamestonk_terminal/options/yfinance_model.py
+++ b/gamestonk_terminal/options/yfinance_model.py
@@ -47,6 +47,24 @@ def get_option_chain(ticker: str, expiration: str) -> pd.DataFrame:
     return chains
 
 
+def get_dividend(ticker: str) -> pd.Series:
+    """Gets option chain from yf for given ticker and expiration
+
+    Parameters
+    ----------
+    ticker: str
+        Ticker to get options for
+
+    Returns
+    -------
+    chains: yf.ticker.Dividends
+        Dividends
+    """
+    yf_ticker = yf.Ticker(ticker)
+    dividend = yf_ticker.dividends
+    return dividend
+
+
 def get_x_values(current_price: float, options: List[Dict[str, int]]) -> List[float]:
     """Generates different price values that need to be tested"""
     x_list = list(range(101))
diff --git a/gamestonk_terminal/options/yfinance_view.py b/gamestonk_terminal/options/yfinance_view.py
index 9f507fdd943..a35e81b102e 100644
--- a/gamestonk_terminal/options/yfinance_view.py
+++ b/gamestonk_terminal/options/yfinance_view.py
@@ -4,7 +4,7 @@ __docformat__ = "numpy"
 import os
 from bisect import bisect_left
 from typing import List, Dict, Any
-from datetime import datetime, date
+from datetime import datetime, date, timedelta
 
 import matplotlib.pyplot as plt
 import numpy as np
@@ -479,9 +479,32 @@ def show_parity(
 
     """
     r_date = datetime.strptime(exp, "%Y-%m-%d").date()
-    delta = (r_date - date.today()).days / 365
-    rate = ((1 + get_rf()) ** delta) - 1
+    delta = (r_date - date.today()).days
+    rate = ((1 + get_rf()) ** (delta / 365)) - 1
     stock = get_price(ticker)
+
+    div_info = yfinance_model.get_dividend(ticker)
+    div_dts = div_info.index.values.tolist()
+
+    if div_dts:
+        last_div = pd.to_datetime(div_dts[-1])
+
+        if len(div_dts) > 3:
+            avg_div = np.mean(div_info.to_list()[-4:])
+        else:
+            avg_div = np.mean(div_info.to_list())
+
+        next_div = last_div + timedelta(days=91)
+        dividends = []
+        while next_div < datetime.strptime(exp, "%Y-%m-%d"):
+            day_dif = (next_div - datetime.now()).days
+            dividends.append((avg_div, day_dif))
+            next_div += timedelta(days=91)
+        div_pvs = [x[0] / ((1 + get_rf()) ** (x[1] / 365)) for x in dividends]
+        pv_dividend = sum(div_pvs)
+    else:
+        pv_dividend = 0
+
     chain = get_option_chain(ticker, exp)
     name = "ask" if ask else "lastPrice"
     o_type = "put" if put else "call"
@@ -495,8 +518,12 @@ def show_parity(
     opts = opts.dropna()
     opts = opts.loc[opts["callPrice"] * opts["putPrice"] != 0]
 
-    opts["callParity"] = opts["putPrice"] + stock - (opts["strike"] / (1 + rate))
-    opts["putParity"] = (opts["strike"] / (1 + rate)) + opts["callPrice"] - stock
+    opts["callParity"] = (
+        opts["putPrice"] + stock - (opts["strike"] / (1 + rate)) - pv_dividend
+    )
+    opts["putParity"] = (
+        (opts["strike"] / (1 + rate)) + opts["callPrice"] - stock + pv_dividend
+    )
 
     diff = o_type + " Difference"
     opts[diff] = opts[o_type + "Price"] - opts[o_type + "Parity"]