python .T.dot() numpy syntax understanding

Question

Might I ask more info about this syntax?

l1.T.dot(l2_delta)

I was under the impression np.dot(x,y) took two arrays as parameters

Does this line means transpose of l1 and then multiply l2_delta still?

Thanks

Answer 1

Your understanding of what your code is doing is correct.

Your confusion is coming from the fact that there are two kinds of numpy "dot" functions:

• The numpy dot function, which takes two arguments:

  • https://docs.scipy.org/doc/numpy/reference/generated/numpy.dot.html

• The dot function that belongs to numpy ndarray objects, which has only one argument:

  • https://docs.scipy.org/doc/numpy-1.10.0/reference/generated/numpy.ndarray.dot.html

Similarly, here's the ".T" function that belongs to ndarray objects: https://docs.scipy.org/doc/numpy/reference/generated/numpy.ndarray.T.html

Answer 2

vec.dot(vec2) == np.dot(vec, vec2)

So yes, you're correct.

https://docs.scipy.org/doc/numpy/reference/generated/numpy.dot.html https://docs.scipy.org/doc/numpy/reference/generated/numpy.matrix.dot.html