Tom's March 20 edit of market.py

examples/market.py

@@ -35,7 +35,7 @@ def consumer_surp(self):
 
     def producer_surp(self):
         "Compute producer surplus"
-        #  == Compute area above supply curve, excluding tax == #
+        #  == Compute area above inverse supply curve, excluding tax == #
         integrand = lambda x: -(self.az/self.bz) + (1/self.bz) * x
         area, error = quad(integrand, 0, self.quantity())  
         return (self.price() - self.tax) * self.quantity() - area

examples/market.py~

@@ -0,0 +1,58 @@
+"""
+Filename: market.py
+Reference: http://quant-econ.net/py/python_oop.html
+"""
+
+from __future__ import division
+from scipy.integrate import quad
+
+class Market:
+
+    def __init__(self, ad, bd, az, bz, tax):
+        """
+        Set up market parameters.  All parameters are scalars.  See
+        http://quant-econ.net/py/python_oop.html for interpretation.
+
+        """
+        self.ad, self.bd, self.az, self.bz, self.tax = ad, bd, az, bz, tax
+        if ad < az:
+            raise ValueError('Insufficient demand.')
+
+    def price(self):
+        "Return equilibrium price"
+        return  (self.ad - self.az + self.bz*self.tax)/(self.bd + self.bz) 
+
+    def quantity(self):
+        "Compute equilibrium quantity"
+        return  self.ad - self.bd * self.price()
+
+    def consumer_surp(self):
+        "Compute consumer surplus"
+        # == Compute area under inverse demand function == #
+        integrand = lambda x: (self.ad/self.bd) - (1/self.bd)* x
+        area, error = quad(integrand, 0, self.quantity())
+        return area - self.price() * self.quantity()
+
+    def producer_surp(self):
+        "Compute producer surplus"
+        #  == Compute area above inverse supply curve, excluding tax == #
+        integrand = lambda x: -(self.az/self.bz) + (1/self.bz) * x
+        area, error = quad(integrand, 0, self.quantity())  
+        return (self.price() - self.tax) * self.quantity() - area
+
+    def taxrev(self):
+        "Compute tax revenue"
+        return self.tax * self.quantity()
+
+    def inverse_demand(self,x):
+        "Compute inverse demand"
+        return self.ad/self.bd - (1/self.bd)* x
+
+    def inverse_supply(self,x):
+        "Compute inverse supply curve"
+        return -(self.az/self.bz) + (1/self.bz) * x + self.tax
+
+    def inverse_supply_no_tax(self,x):
+        "Compute inverse supply curve without tax"
+        return -(self.az/self.bz) + (1/self.bz) * x
+