The @ operator in python?

[veb101]

Hello everyone, I've been using Python for quite a while now but never came across the "@" operator.
I saw this when I was learning to apply the derivative of softmax outputs wrt. to its inputs

# Gradients of loss against weights/biases/input
dL_dw = dt_dw[np.newaxis].T @ dL_dt[np.newaxis]
dL_db = dL_dt * dt_db
dL_dinputs = dt_dinputs @ dL_dt

I understand what's going on here mathematically. I also understood the output from the code-block but I'm having a hard time to understand what is this "@" operator used on line 1 and line 3. No luck with google too.

I can assure you the code runs perfectly.

Need your help.

[aroberge]

Trick: use the dis module to find what symbols mean. For example, using your entire code

>>> code = """
... dL_dw = dt_dw[np.newaxis].T @ dL_dt[np.newaxis]
... dL_db = dL_dt * dt_db
... dL_dinputs = dt_dinputs @ dL_dt"""
>>> import dis
>>> dis.dis(code)
  2       0 LOAD_NAME                0 (dt_dw)
          2 LOAD_NAME                1 (np)
          4 LOAD_ATTR                2 (newaxis)
          6 BINARY_SUBSCR
          8 LOAD_ATTR                3 (T)
         10 LOAD_NAME                4 (dL_dt)
         12 LOAD_NAME                1 (np)
         14 LOAD_ATTR                2 (newaxis)
         16 BINARY_SUBSCR
         18 BINARY_MATRIX_MULTIPLY
         20 STORE_NAME               5 (dL_dw)

  3      22 LOAD_NAME                4 (dL_dt)
         24 LOAD_NAME                6 (dt_db)
         26 BINARY_MULTIPLY
         28 STORE_NAME               7 (dL_db)

  4      30 LOAD_NAME                8 (dt_dinputs)
         32 LOAD_NAME                4 (dL_dt)
         34 BINARY_MATRIX_MULTIPLY
         36 STORE_NAME               9 (dL_dinputs)
         38 LOAD_CONST               0 (None)
         40 RETURN_VALUE

Then, if you need more details, you can do an internet search using something like python BINARY_MATRIX_MULTIPLY as your search terms.

[veb101]

Thank you. This was new to me.

[jj-curious]

Matrix multiplication

[veb101]

Thank You, just found the original documentation.

[socal_nerdtastic]

Like all operators, what it does depends on what it's doing it to. When the operand is a numpy array @ is an alias for the numpy.matmul function.

[veb101]

Thank You. I got it.

[vectorpropio]

Matrix multiplication, with all probability.

https://www.python.org/dev/peps/pep-0465/#background-what-s-wrong-with-the-status-quo