In order to package the object-oriented drawing library into a call interface that only uses functions, the pyplot module internally saves the current chart and current sub-picture and other information. The current chart and sub-graph can be obtained using plt.gcf () and plt.gca (), which means "Get Current Figure" and "Get Current Axes", respectively. In the pyplot module, many functions deal with the current Figure or Axes objects, for example:
plt.plot () will actually get the current Axes object ax through plt.gca (), and then call the ax.plot () method to realize the real drawing.
np.r_: is to connect two matrices by column, that is, add the two matrices up and down, requiring the number of columns to be equal, similar to concat () in pandas.
np.c_: connect two matrices by row, that is, add the two matrices to the left and right, requiring the number of rows to be equal, similar to merge () in pandas.
dZ2 = np.multiply (dA2, np.int64 (A2> 0)) After
debugging, np.int64 (A2> 0) generates a matrix with the same dimensions as A2. If the condition (A2> 0) is met, it is 1, which is not satisfied Then 0
Insert picture description here
