The value of total_sales in step 15 seem to be incorrect

Projects
1

In step 15, it asks me to print total_sales and it prints out 1498.7400000000005. The same happens in the project walkthrough. However, I noticed that there isn’t any number in the list sales with more than 2 decimals. There must be a problem, but I don’t know where.

2

Since we are printing, then we can represent numbers as strings using string formatting.

>>> a = 1498.7400000000005
>>> print (f'{a:.2f}')    # f-string formatting
1498.74
>>> print ('{:.2f}'.format(a))    # .format() method
1498.74
>>> print ('%.2f' % a)    # modulo formatting (legacy C)
1498.74
>>>
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3

I wasn’t asking about that. It’s just that since there isn’t any number with more than two decimals, it’s just impossible for their sum to have so many decimals and be 1498.7400000000005

4

This has something to do with the way float type values are stored in the computer’s memory. That means you do sometimes get rounding errors like this.

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5

This is a really important error. It’s strange it isn’t fixed.

6

It isn’t an error with the CC lesson. It is the way floats are handled in the memory of a computer. Sorry, but that’s as far as my CS knowledge takes me.

7

It is not fixable since it is the nature of binary arithmetic. Google floating point arithmetic and see if you can come up with a solution. Hint: There is none. We need to learn how to address this in our programs. I gave you a way to represent that number as currency. Play around with other methods and see what you come up with.

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8

Strange…but true…

I just multiplied by 100 and then created a second variable called ‘grand_total_sales’:

for sale in sales: total_sales+=(float((sale[1:]))*100) grand_total_sales=total_sales/100 print(grand_total_sales)