Lab: calculate discounts

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I'm doing an exercise and so far so good as the code (after some help from other threads) now works almost fine, but...can't get the right results as a math point of view.

Here it's the code:

#getting base prices from user
item1 = float(input('Enter the price of the first item: '))
item2 = float(input('Enter the price of the second item: '))
clubc = raw_input('Does customer have a club card? (Y/N): ')
tax = float(input('Enter tax rate, e.g. 5.5 for 5.5% tax: '))
basep = (item1 + item2)
print('Base price = ', basep)

#setting variables for calculation
addtax = (1 + (tax / 100))

#conditions for output
if item1 >= item2 and clubc == 'N':
    priceafterd = float(item1 + (item2 / 2))
    print('Price after discounts = ', priceafterd)
    totalprice = (priceafterd * addtax)
    print('Total price = ', totalprice)
elif item2 >= item1 and clubc == 'N':
    priceafterd = float(item2 + (item1 / 2))
    print('Price after discounts = ', priceafterd)
    totalprice = (priceafterd * addtax)
    print('Total price = ', totalprice)

if item1 >= item2 and clubc == 'Y':
    priceafterd = float((item1 + (item2 / 2)) * 0.9)
    print('Price after discounts = ', priceafterd)
    totalprice = (priceafterd * var3)
    print('Total price = ' + totalprice)
else:
    priceafterd = float((item2 + (item1 / 2)) * 0.9)
    print('Price after discounts = ', priceafterd)
    totalprice = (priceafterd * var3)
    print('Total price = ' + totalprice)

The exercise requires to write a program that computes how much a customer has to pay after purchasing two items, depending on a promo, club card and taxes.

The problem is with the results. As an example of inputs:

Enter price of the first item: 10
Enter price of the second item: 20
Does customer have a club card? (Y/N): y
Enter tax rate, e.g. 5.5 for 5.5% tax: 8.25
Base price = 30.00
Price after discounts = 22.50
Total price = 24.36

Instead, I got:

line 33, in <module>
print('Total price = ' + totalprice)
TypeError: cannot concatenate 'str' and 'float' objects

What's wrong with the syntax? Thanks a lot!

python-2.x python
1 Answers

The problem

In the second conditional you wrote print('Total price = ' + totalprice) line instead of the print('Total price = ', totalprice), and the problem is in that:

totalprice has float type, meanwhile 'Total price = ' is the str and what you are trying to do is almost like str() + float(), and because python doesn't know how to concatenate string and float number it raises an exception.

How to solve

1) Use the same print('Total price = ', totalprice) line everywhere

Why does it work and print('Total price = ' + totalprice) does not?

Because print automatically converts everything to string representation, you can imagine print('Total price = ', totalprice) expression like that:

print(str('Total price = ') + " " + str(totalprice))

2) Convert float to str and concatenate strs

print('Total price = ' + str(totalprice))

str(totalprice) converts totalprice from float to the str and python knows how to concatenate strings together.

3) Formatting

"Total price = {}".format(3.14)" is equivalent to the "Total price = 3.14" string,
so print("Total price = {}".format(totalprice)) also will work

in python 3 we also have f-stings:

f"Total price = {3.14}" == "Total price = 3.14"

print(f"Total price = {totalprice}")

user_121419490
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