How to get NaN when I divide by zero

Question

When I do floating point division in Python, if I divide by zero, I get an exception:

>>> 1.0/0.0
Traceback (most recent call last):
  File \"

        

Answer 1

Method 1:

try:
    value = a/b
except ZeroDivisionError:
    value = float('Inf')

Method 2:

if b != 0:
    value = a / b
else:
    value = float('Inf')

But be aware that the value could as well be -Inf, so you should make a more distinctive test. Nevertheless, this above should give you the idea how to do it.

Answer 2

If i understand your problem properly then this should be the solution:

try:
   1.0/0.0
except:    
   return 'inf'

you can modified it according to various python exception handling method available

Answer 3

You could try using the 'decimal' module:

>>> from decimal import *
>>> setcontext(ExtendedContext)
>>> inf = Decimal(1) / Decimal(0)
>>> print(inf)
Infinity
>>> neginf = Decimal(-1) / Decimal(0)
>>> print(neginf)
-Infinity
>>> print(neginf + inf)
NaN
>>> print(neginf * inf)
-Infinity
>>> print(dig / 0)
Infinity

Answer 4

I used a wrapper function in a python program of mine for a simple division that was returning ZeroDivisionError when the sensors I was using weren't plugged in. It simply returns 0 (zero), which in real-world terms is what I wanted. Probably gets messy with more variables, however...

def calculation(a, b):
    if a == 0:
        return 0
    elif b == 0:
        return 0
    else:
        return a/b

Answer 5

The easiest way to get this behaviour is to use numpy.float64 instead of Python default float type:

>>> import numpy
>>> numpy.float64(1.0) / 0.0
inf

Of course this requires NumPy. You can use numpy.seterr() to fine-tune the error handling.