#Future Value
#It is difficult to make a budget that spans several years,
#because prices are not stable. If your company needs 200 pencils
#per year, you cannot simply use this year's price as the cost of
#pencils two years from now. Because of inflation the cost is likely
#to be higher than it is today.
#
#Write a program to gauge the expected cost of an item in a specified
#number of years. The program asks for the cost of the item,
#the number of years from now that the item will be purchased,
# and the rate of inflation. The program then outputs the estimated
#cost of the item after the specified period.
#Have the user enter the inflation rate as a percentage, like 5.6 (%).
#Your program should then convert the percent to a fraction, like 0.056,
#and should use a loop to estimate the price adjusted for inflation.
from graphics import *
def main():
print("This program calculates the expected price of an item")
price = eval(input("Please, input the today's price of an item: "))
years = eval(input("Please, input the number of years from now that the item will be purchased: "))
inflation = eval(input("Please, input the inflation rate: "))
starting_price = price # preserving the starting price
# calculating the price in ... years
inflation = inflation/100.0
for i in range(years):
price=price+price*inflation
#print("price = ", price)
phrase = "The starting price is $"+str(starting_price)+",\n In "+\
str(years)+" years the price will be $"+str(round(price,2))
print(phrase)
print("\n \t Now let's do it in graphics!")
window = GraphWin('Predicting item\'s price.',800,600)
window.setBackground("white")
#Displaying the result in the graphics window
PriceText = Text(Point(400,450),phrase)
PriceText.draw(window)
# let's draw the scale consisting of five marks(you may skip this part till drawing bars):
print("calculations:")
diff = price-starting_price # calculating the difference in starting price and final price
scale=diff/4.# dividing by four, since we'll have 5 marks;
print("difference = ",diff)
print("scale = ",scale)
l1='$'+str(round(starting_price,2)) # converting numerical mark to string
print("label 1=",l1)
label2=starting_price+scale
l2='$'+str(round(label2,2)) # converting numerical mark to string, rounding off to two decimal places
print("label 2=",l2)
label3=starting_price+2*scale
l3='$'+str(round(label3,2)) # converting numerical mark to string, rounding off to two decimal places
print("label 3=",l3)
label4=starting_price+3*scale
l4='$'+str(round(label4,2)) # converting numerical mark to string, rounding off to two decimal places
print("label 4=",l4)
label5=starting_price+4*scale
l5='$'+str(round(label5,2)) # converting numerical mark to string, rounding off to two decimal places
print("label 5",l5)
# displaying labels and lines
Text(Point(40,30), l5).draw(window)
Line(Point(70,30),Point(580,30)).draw(window)
Text(Point(40,80), l4).draw(window)
Line(Point(70,80),Point(580,80)).draw(window)
Text(Point(40,130),l3).draw(window)
Line(Point(70,130),Point(580,130)).draw(window)
Text(Point(40,180),l2).draw(window)
Line(Point(70,180),Point(580,180)).draw(window)
Text(Point(40,230),l1).draw(window)
Line(Point(70,230),Point(580,230)).draw(window)
# draw bars for successive years
price = starting_price # re-assigning price to initial one
# need variable pixels to find the bar height
pixels=(50.)/scale # calculating how many pixels should be used to 1$
print("pixels=" ,pixels)
bar_width = 40
for i in range(years):
price = price + price*inflation # calculating price in a year
print("price=", price)
# draw bar for this value
x = i * bar_width + 180 # x-coordinate of the bottom left
#corner of the bar
height=(price-starting_price)*pixels # calculating the height of the
# bar so that it corresponds to the difference between
# previous year's price and current year's price
print("height=",height)
bar=Rectangle(Point(x,230),Point(x+bar_width,230-height))
bar.setFill('green')
bar.setWidth(1)
bar.draw(window)
# putting label under the bar with the corresponind price
T = Text(Point(x+bar_width/2,260),str(round(price,1)))
T.draw(window)
T = Text(Point(400,500),"Click anywhere to terminate the program.")
T.draw(window) # drawing the text
window.getMouse() # waiting for a mouse click
window.close()
main()