Add rebalancer.py

Author: desimmons

README.rst

@@ -34,12 +34,28 @@ portfolio_rebalance
 ===================
 
 
-    Add a short description here!
+    Understand how to rebalance your UK Vanguard portfolio using switch procedures.
 
 
-A longer description of your project goes here...
+This file performs portfolio rebalancing calculations, presenting the results
+confluent with Vanguard Switch procedures. It _does not_ interact directly with 
+your Vanguard account. For example, if you hold
+assets "A", "B", and "C" on Vanguard, each with total values in your
+portfolio of 2000, 3000, and 4000, respectively. By running:
+`rebalance A 2000 B 3000 C 4000`
+You will be presented with:
+`{'A': 1.0, 'B': 0.0, 'C': -0.25}`,
+indicating that you should sell 25% of "C", placing 100% of the sale
+into "A" and 0% into "B".
 
 
+Install and run
+===============
+
+1. Ensure you have `pip` installed
+2. `pip install .`
+3. `rebalance <Asset A> <Total value of asset A in your portfolio> ... <Asset Z> <Total value of asset Z in your portfolio>
+
 .. _pyscaffold-notes:
 
 Note

setup.cfg

@@ -72,8 +72,8 @@ testing =
 # console_scripts =
 #     script_name = portfolio_rebalance.module:function
 # For example:
-# console_scripts =
-#     fibonacci = portfolio_rebalance.skeleton:run
+console_scripts =
+    rebalance = portfolio_rebalance.rebalance:run
 # And any other entry points, for example:
 # pyscaffold.cli =
 #     awesome = pyscaffoldext.awesome.extension:AwesomeExtension

src/portfolio_rebalance/rebalance.py

@@ -0,0 +1,100 @@
+"""
+This file performs portfolio rebalancing, presenting the results
+confluent with Vanguard Switch procedures. For example, if you hold
+assets "A", "B", and "C" on Vanguard, each with total values in your
+portfolio of 2000, 3000, and 4000, respectively. By running:
+`rebalance A 2000 B 3000 C 4000`
+You will be presented with:
+`{'A': 1.0, 'B': 0.0, 'C': -0.25}`,
+indicating that you should sell 25% of "C", placing 100% of the sale
+into "A" and 0% into "B".
+"""
+
+import sys
+
+from portfolio_rebalance import __version__
+
+__author__ = "David Simmons"
+__copyright__ = "David Simmons"
+__license__ = "MIT"
+
+
+def rebalance(dict):
+    """Portfolio rebalancer
+
+    Args:
+      kwargs (Dict): Dictionary of assets and total portfolio value
+
+    Returns:
+      Dict: Dictionary of assets and percentage to be sold/bought 
+    """
+    total = 0.0 
+    for key, value in dict.items():
+        total += value
+
+    rebalanced_asset_value = total / len(dict)
+    rebalanced_assets = {}
+
+    for key, value in dict.items():
+        rebalanced_assets[key] = rebalanced_asset_value / dict[key] - 1
+    
+    value_of_buys = 0
+    for key, value in rebalanced_assets.items():
+        if value > 0:
+            value_of_buys += value
+        else:
+            pass
+
+    for key, value in rebalanced_assets.items():
+        if value > 0:
+            print(value)
+            rebalanced_assets[key] /= value_of_buys
+        else:
+            pass
+
+    return rebalanced_assets
+
+def parse_args(args):
+    """Parse command line parameters
+
+    Args:
+      args (List[str]): command line parameters as list of strings
+          (for example  ``["--help"]``).
+
+    Returns:
+      :obj:`argparse.Namespace`: command line parameters namespace
+    """
+    keys = []
+    values = []
+    for asset in args:
+        try:
+            is_float = float(asset)
+        except ValueError:
+            is_float = False
+        if isinstance(asset, str) and not is_float:
+            keys.append(asset)
+        elif is_float:
+            values.append(float(asset))
+        else:
+            raise Exception()
+    if len(keys) != len(values):
+        raise Exception()
+    
+    assets = {}
+    for idx, el in enumerate(keys):
+        assets[el] = values[idx]
+            
+    return assets
+
+
+def main(args):
+    kwargs = parse_args(args)
+    print(rebalance(kwargs))
+
+
+def run():
+    main(sys.argv[1:])
+
+
+if __name__ == "__main__":
+    run()