Python math is wrong [duplicate]

Answer 1

You have reached a new level in computer science, and you are coming of age.

You therefore are now ready for the next step. I have been authorized by the BDFL himself to reveal the following Super Secret document to you. The ancients understood it and deciphered it first, and now, so will you!

The Floating Point Guide

Treat this document with care! Only share this with people you know have reached the same baffling conclusions!

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Answer 2

For a painfully-rigorous guide to how floating-point arithmetic works, complete instructions on how to calculate how large the errors in your answers will be, you need:

What Every Computer Scientist Should Know About Floating-Point Arithmetic

Once you've read that, you should go and look for notes on the 8087 specifically, because it implements IEEE 754 poorly and this can cause new exciting problems in your life.