When is a Python Overflow Error generated?

Question

Why do the below three lines produce different output in python3, despite the values being equal?

>>> 10 ** 500
100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

>>>1E500
inf

>>>1E250 ** 2
---------------------------------------------------------------------------
OverflowError                             Traceback (most recent call last)
<ipython-input-110-d71dbae32ab9> in <module>
----> 1 1E250**2

Tim Roberts · Accepted Answer · 2022-03-21 22:22:01Z

3

They are not equal. The first is an integer, and Python allows integers to be infinitely large. (Well, virtually infinite.) The other two are floating point numbers, and the value is beyond the range of a double. The 1E500 value is a constant, and overflows in constants result in the inf pseudo-value. The final one is an arithmetic operation, and Python detects and throws overflows in arithmetic operations.

answered Mar 21, 2022 at 22:22

Tim Roberts

55.3k4 gold badges28 silver badges41 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

jgg Over a year ago

Thanks for the explanation. Why is it that the values are not equal? I see that these numbers are of different types but the numerical values are equivalent at least in a mathematical sense (i.e. 10 == 10.0).

Tim Roberts Over a year ago

The world of floating point numbers is a strange and magical one. They are stored in binary, so it's actually N x 2**M, and you only have 54 bits available for N. So, except for a rather narrow list of small integers, floating point values are always approximations. Try doing int(1E100) to see that. That's the closest multiple of a power of 2 you can get, but it only has 17 valid digits.

Collectives™ on Stack Overflow

When is a Python Overflow Error generated?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related