I'm in trouble. Decimal numbers don't come when I do math - numbers

Question

def call_result(label_result, n1, n2, n3):
num1 = (n1.get())
num2 = (n2.get())
num3 = (n3.get())
num4 = 100
num5 = 12
num6 = 2
main1 = float(int(num1))*float(int(num2)) / 12 / 2 / 100
main2 = float(int(num1)) / float(int(num3))
main3 = float(int(main2))+float(int(main1))
label_result.config(text="Result = %d" % float(main3))
return
I'm in trouble. Decimal numbers don't come when I do math
The answer is supposed to be 20.84 but this code produces 20.

Answer 1

The problem is due to the conversion between int and float
Assuming the three nums are strings you should just convert them to float directly and skip the intermediate step.
Moreover when you convert from float to int and then back to float you lost the decimal data because int does not store it.
For example
main2 = 23.34 # main2 is a float with value 23.34
main2 = int(main2) # main2 is now an int with value 23
# Remember int (short for integer) cannot store floating point values and will truncate the number to make an integer
main2 = float(main2) # main2 is now a float but the value is 23.0 because you lost the precision when it was converted to int
I recommend doing something like this
def call_result(label_result, n1, n2, n3):
num1 = float(n1.get())
num2 = float(n2.get())
num3 = float(n3.get())
num4 = 100
num5 = 12
num6 = 2
main1 = num1 * num2 / 12 / 2 / 100
main2 = num1 / num3
main3 = main2 + main1
label_result.config(text="Result = %.2f" % main3)
return
Another thing to take care of is the format specifier you use for the string. %d refers to an integer while %f is for floats. Even if main3 was a float you would have ended up with an integer in your string.
%.2f will truncate a float to a precision of 2 decimal places
"%.2f" % 123.45678 becomes 123.45
Take a look at the string formatting guide here