Find the min/max excluding zeros in a numpy array (or a tuple) in python

Question

I have an array. The valid values are not zero (either positive or negetive). I want to find the minimum and maximum within the array which should not take zeros into accoun

Answer 1

If you can choose the "invalid" value in your array, it is better to use nan instead of 0:

>>> a = numpy.array([1.0, numpy.nan, 2.0])
>>> numpy.nanmax(a)
2.0
>>> numpy.nanmin(a)
1.0

If this is not possible, you can use an array mask:

>>> a = numpy.array([1.0, 0.0, 2.0])
>>> masked_a = numpy.ma.masked_equal(a, 0.0, copy=False)
>>> masked_a.max()
2.0
>>> masked_a.min()
1.0

Compared to Josh's answer using advanced indexing, this has the advantage of avoiding to create a copy of the array.