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pythoninfinity

Python Infinity - Any caveats?

So Python has positive and negative infinity:

float("inf"), float("-inf")

This just seems like the type of feature that has to have some caveat. Is there anything I should be aware of?

Solution

  • You can still get not-a-number (NaN) values from simple arithmetic involving inf:

    >>> 0 * float("inf")
nan

    Note that you will normally not get an inf value through usual arithmetic calculations:

    >>> 2.0**2
4.0
>>> _**2
16.0
>>> _**2
256.0
>>> _**2
65536.0
>>> _**2
4294967296.0
>>> _**2
1.8446744073709552e+19
>>> _**2
3.4028236692093846e+38
>>> _**2
1.157920892373162e+77
>>> _**2
1.3407807929942597e+154
>>> _**2
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
OverflowError: (34, 'Numerical result out of range')

    The inf value is considered a very special value with unusual semantics, so it's better to know about an OverflowError straight away through an exception, rather than having an inf value silently injected into your calculations.