Python – How to Get NaN When Dividing by Zero

python

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 "<stdin>", line 1, in <module>
ZeroDivisionError: float division

I'd really like to get NaN or Inf instead (because the NaN or Inf will propagate through the rest of my calculation correctly and not kill my program).

How can I do this?

Best Answer

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.

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Use math.isnan:

>>> import math
>>> x = float('nan')
>>> math.isnan(x)
True

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Where A is your 2D array:

import numpy as np
A[np.isnan(A)] = 0

The function isnan produces a bool array indicating where the NaN values are. A boolean array can by used to index an array of the same shape. Think of it like a mask.

Best Answer

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