Describe the issue:

numpy.random.mtrand.RandomState.dirichlet no longer accepts alpha(count)-values that are zero.

With older (e.g. 1.11.3) versions of numpy, dirichlet accepted zero as an alpha(count) value.

numpy.version
'1.11.3'
dirichlet([5,9,0,8])
array([ 0.17970351, 0.35902845, 0. , 0.46126803])
dirichlet([5,9,0,8])
array([ 0.15228294, 0.45822224, 0. , 0.38949482])

With newer (e.g. 1.21.5) versions of numpy, alpha(count) values must be greater than zero. Very small real-values are accepted.

numpy.version
'1.21.5'
dirichlet([5,9,0.000001,8])
array([0.38285451, 0.26206592, 0. , 0.35507958])
dirichlet([5,9,0,8])
Traceback (most recent call last):
File "", line 1, in
File "mtrand.pyx", line 4390, in numpy.random.mtrand.RandomState.dirichlet
ValueError: alpha <= 0

I have some applications where alpha(count|)-values are raw-data and zero is a very valid value. These applications worked with old versions of numpy but not with newer versions.

Reproduce the code example:

dirichlet([5,9,0,8])

Error message:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "mtrand.pyx", line 4390, in numpy.random.mtrand.RandomState.dirichlet
ValueError: alpha <= 0

NumPy/Python version information:

1.21.5

Context for the issue:

I have some applications where alpha(count|)-values are raw-data and zero is a very valid value. These applications worked with old versions of numpy but not with newer versions.