There's something wrong with my understanding of either the round function in python or how doubles are represented in python. I find a very perplexing behavior when rounding numbers that have a double precision rounding error; for example 1.01046+.00002=1.0104799999999998. When I round this to 5 digits, python reports the result as 1.01048, the expected result. But I thought the whole issue was that 1.01046+.00002=1.0104799999999998 because there's no double value that exactly equals 1.01048. If round takes in a double and returns a double, how can it return 1.01048 if no such double exists?
The following code:print([1.01046+.00002*i for i in range(6)])
outputs:[1.01046, 1.0104799999999998, 1.0105, 1.0105199999999999, 1.01054, 1.01056]
wheras this code:print([round(1.01046+.00002*i,5) for i in range(6)])
outputs:[1.01046, 1.01048, 1.0105, 1.01052, 1.01054, 1.01056]
why is it that python doesn't have an exact value for 1.01046+.00002*1, python says "I don't have any such number; I can give you a number that's really close though", but when I ask python to round the resulting number, it goes "oh yeah of course that's 1.01048"