Develop a widget class Finances that incorporates a calculator and a tool to com- pute the monthly mortgage. In your implementation, you should use the Calc class devel- oped in the case study and a Mortgage widget from Problem 9.17.

Augment calculator widget Calc so that the user can type keyboard keys instead of clicking buttons corresponding to the 10 digits, the dot ., and the operators +, -, *, and /.

Also allow the user to type the Enter/Return key instead of clicking button labeled =.

above are the questions and below is my calculator code, I dont know how to answer the above in python.

from tkinter import Tk, Button, Frame, Entry, END, RIDGE, RAISED

from math import sqrt

class Calc(Frame):

'a simple calculator'

def __init__(self,parent=None):

'calculator constructor'

Frame.__init__(self,parent)

self.memory = '' # memory storage

self.expr = '' # current expression storage

self.startOfNextOperand = True # start of new operand

# use Entry widget for display

self.entry = Entry(self, relief=RIDGE, borderwidth=3,

width=20, bg='gray',

font=('Helvetica', 18))

self.entry.grid(row=0, column=0, columnspan=5)

# calculator button labels in a 2D list

buttons = [['MC', 'M+', 'M-', 'MR'],

['C' , '\u221a', 'x\u00b2', '+' ],

['7' , '8' , '9' , '-' ],

['4' , '5' , '6' , '*' ],

['1' , '2' , '3' , '/' ],

['0' , '.' , '+-', '=' ]]

# create and place buttons in appropriate row and column

for r in range(6):

for c in range(4):

# function cmd() is defined so that when it is

# called without an input argument, it executes

# self.click(buttons[r][c])

def cmd(x=buttons[r][c]):

self.click(x)

b = Button(self, # button for symbol buttons[r][c]

text=buttons[r][c],

width=3,

relief=RAISED,

command=cmd) # cmd() is the handler

b.grid(row= r +1, column=c) # entry is in row 0

def click(self, key):

'handler for event of pressing button labeled key'

if key == '=':

# evaluate the expression, including the value

# displayed in entry and display result

try:

result = eval(self.expr + self.entry.get())

self.entry.delete(0, END)

self.entry.insert(END, result)

self.expr = ''

except:

self.entry.delete(0, END)

self.entry.insert(END, 'Error')

elif key in '+*-/':

# add operand displayed in entry and operator key

# to expression and prepare for next operand

self.expr += self.entry.get()

self.expr += key

self.startOfNextOperand = True

elif key == '\u221a':

# compute and display square root of entry

result = sqrt(eval(self.entry.get()))

self.entry.delete(0, END)

self.entry.insert(END, result)

elif key == 'x\u00b2':

# compute and display the square of entry

result = eval(self.entry.get() ) **2

self.entry.delete(0, END)

self.entry.insert(END, result)

elif key == 'C':

# clear entry

self.entry.delete(0, END)

elif key in {'M+', 'M-'}:

# add or subtract entry value from memory

self.memory = str(eval(self.memory + key[1] + self.entry.get()))

elif key == 'MR':

# replace value in entry with value stored in memory

self.entry.delete(0, END)

self.entry.insert(END, self.memory)

elif key == 'MC':

# clear memory

self.memory = ''

elif key == '+-':

# switch entry from positive to negative or vice versa

# if there is no value in entry, do nothing

try:

if self.entry.get()[0] == '-':

self.entry.delete(0)

else:

self.entry.insert(0, '-')

except IndexError:

pass

else:

# insert digit at end of entry, or as the first

# digit if start of next operand

if self.startOfNextOperand:

self.entry.delete(0, END)

self.startOfNextOperand = False

self.entry.insert(END, key