Python: 50*1.1 = 55.0000000001?

Question

See the code below. I suspect there are other similar cases.
Due to the trailing decimal, certain calculations become tricky and somewhat unpredictable . E.g. math.ceil(50*1.1) turns out to be 56, which is incorrect.
My questions:
1. Under what circumstances should I expect this type of cases to occur?
2. What's the best way to deal with this?
Thanks.

https://code.sololearn.com/c6ywYjHUGjKW/?ref=app

Answer 1

The error is caused by floating point arithmetics and is a known problem.
Is the precision relevant for your purposes? If your answer is 'yes' then you should get familiar with the 'decimal'-module. This is especially e.g. for calculations in the financial sector which has high precision demands.

To solve these and similar tasks, many universities offering computer science programs have an "Institute for Fault Tolerance." If not, then the field of study is integrated into another institute. This shows that this is a steady field of scientific research.

Answer 2

It is inherent to how computers represent numbers, hence it is not quite an error.

Floats should not be compared with "==", unless taking floating point limitations into consideration.

https://www.sololearn.com/Discuss/3226502/?ref=app

Answer 3

Thank you. Very informative.