Add docstrings + add ability to set matplotlib backend.

gamestonk_terminal/backtesting/bt_controller.py

@@ -73,18 +73,21 @@ class BacktestingController:
         return True
 
     def call_ema(self, other_args: List[str]):
+        """Call EMA strategy"""
         bt_view.simple_ema(self.ticker, self.start, other_args)
 
     def call_ema_cross(self, other_args: List[str]):
+        """Call EMA Cross startegy"""
         bt_view.ema_cross(self.ticker, self.start, other_args)
 
     def call_rsi(self, other_args: List[str]):
+        """Call RSI Strategy"""
         bt_view.rsi_strat(self.ticker, self.start, other_args)
 
 
 def menu(ticker: str, start: Union[str, datetime]):
     """Technical Analysis Menu"""
-
+    plt.close("all")
     bt_controller = BacktestingController(ticker, start)
     bt_controller.call_help(None)
 

gamestonk_terminal/backtesting/bt_helper.py

@@ -4,18 +4,43 @@ __docformat__ = "numpy"
 
 from datetime import datetime
 from typing import Union
+import matplotlib
 from matplotlib import pyplot as plt
 from pandas.plotting import register_matplotlib_converters
 import bt
 from gamestonk_terminal.helper_funcs import plot_autoscale
-from gamestonk_terminal.config_plot import PLOT_DPI
+from gamestonk_terminal.config_plot import PLOT_DPI, backend
 from gamestonk_terminal import feature_flags as gtff
 
 register_matplotlib_converters()
 
+if backend is not None:
+    print(f"Setting matplotlib backend to {backend}")
+    matplotlib.use(backend)
+
+if matplotlib.get_backend() in ["Agg", "MacOSX"]:
+    print(
+        "You may encounter errors due to your MatplotLib backend. "
+        " Please configure in config_plot.py."
+    )
+
 
 def buy_and_hold(ticker: str, start: Union[str, datetime], name: str):
-    """Generates a backtest object for the given ticker"""
+    """
+    Generates a backtest object for the given ticker
+    Parameters
+    ----------
+    ticker: str
+        Stock to test
+    start: Union[str, datetime]
+        Backtest start date.  Can be either string or datetime
+    name:
+        Name of teh backtest (for labeling purposes)
+
+    Returns
+    -------
+    bt.Backtest object for buy and hold strategy
+    """
     prices = bt.get(ticker, start=start)
     bt_strategy = bt.Strategy(
         name,
@@ -40,6 +65,7 @@ def plot_bt(res: bt.backtest.Result, plot_title: str):
         Title of plot
 
     """
+    matplotlib.use("TkAgg")
     _, ax = plt.subplots(figsize=plot_autoscale(), dpi=PLOT_DPI)
     res.plot(title=plot_title, ax=ax)
     plt.grid(b=True, which="major", color="#666666", linestyle="-")

gamestonk_terminal/backtesting/bt_view.py

@@ -11,7 +11,21 @@ from gamestonk_terminal.backtesting.bt_helper import buy_and_hold, plot_bt
 
 
 def simple_ema(ticker: str, start_date: Union[str, datetime], other_args: List[str]):
+    """
+    Strategy where stock is bought when Price > EMA(l)
+    Parameters
+    ----------
+    ticker: str
+        Stock to test
+    start: Union[str, datetime]
+        Backtest start date.  Can be either string or datetime
+    other_args: List[str]
+        List of argparse arguments
 
+    Returns
+    -------
+    Plot and a printout of backtest
+    """
     parser = argparse.ArgumentParser(add_help=False, prog="ema")
     parser.add_argument(
         "-l", default=20, dest="length", type=int, help="EMA period to consider"
@@ -77,6 +91,21 @@ def simple_ema(ticker: str, start_date: Union[str, datetime], other_args: List[s
 
 
 def ema_cross(ticker: str, start_date: Union[str, datetime], other_args: List[str]):
+    """
+    Strategy where we go long/short when EMA(short) is greater than/less than EMA(short)
+    Parameters
+    ----------
+    ticker: str
+        Stock to test
+    start: Union[str, datetime]
+        Backtest start date.  Can be either string or datetime
+    other_args: List[str]
+        List of argparse arguments
+
+    Returns
+    -------
+    Plot and a printout of backtest
+    """
     parser = argparse.ArgumentParser(add_help=False, prog="ema_cross")
     parser.add_argument(
         "-l", "--long", default=50, dest="long", type=int, help="Long EMA period"
@@ -164,6 +193,21 @@ def ema_cross(ticker: str, start_date: Union[str, datetime], other_args: List[st
 
 
 def rsi_strat(ticker: str, start_date: Union[datetime, str], other_args: List[str]):
+    """
+    Strategy that buys when the stock is less than a threshold and shorts when it exceeds a threshold.
+    Parameters
+    ----------
+    ticker: str
+        Stock to test
+    start: Union[str, datetime]
+        Backtest start date.  Can be either string or datetime
+    other_args: List[str]
+        List of argparse arguments
+
+    Returns
+    -------
+    Plot and a printout of backtest
+    """
     parser = argparse.ArgumentParser(add_help=False, prog="rsi_strat")
     parser.add_argument(
         "-p",

gamestonk_terminal/config_plot.py

@@ -1,5 +1,19 @@
 PLOT_DPI = 100
 
+# Backend to use for plotting.  After using the bt library, which somehow changes the
+# backend to 'agg' it raises an error.  Set this to avoid.
+"""
+More information:
+https://matplotlib.org/stable/tutorials/introductory/usage.html#the-builtin-backends
+
+Common ones:
+module://backend_interagg   : This is what pycharm defaults to in Scientific Mode
+MacOSX   : Mac default.  Does not work with backtesting
+tkAgg : This uses the tkinter library.
+Qt5Agg  : This requires the PyQt5 package is installed
+"""
+backend = None
+
 # Used when USE_PLOT_AUTOSCALING is set to False
 PLOT_HEIGHT = 500
 PLOT_WIDTH = 800