string representation of a numpy array with commas separating its elements

Question

I have a numpy array, for example:

points = np.array([[-468.927,  -11.299,   76.271, -536.723],
                   [-429.379, -694.915, -214.689,  745.763],         


        

Answer 1

The function you are looking for is np.set_string_function. source

What this function does is let you override the default __str__ or __repr__ functions for the numpy objects. If you set the repr flag to True, the __repr__ function will be overriden with your custom function. Likewise, if you set repr=False, the __str__ function will be overriden. Since print calls the __str__ function of the object, we need to set repr=False.

For example:

np.set_string_function(lambda x: repr(x), repr=False)
x = np.arange(5)
print(x)

will print the output

array([0, 1, 2, 3, 4])

A more aesthetically pleasing version is

np.set_string_function(lambda x: repr(x).replace('(', '').replace(')', '').replace('array', '').replace("       ", ' ') , repr=False)

print(np.eye(3))

which gives

[[1., 0., 0.],
 [0., 1., 0.],
 [0., 0., 1.]]

Hope this answers your question.