Numpy——2. Shape of array

The shape of the array

View the shape of the array

a.shape()
You can judge how many dimensions the array is by the number of returned values

Modify the shape of the array

a.reshape(x, y) Return value but not modified a Array
a.flatten() Turn the array directly into one dimension
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The calculation of array

Calculation of arrays and numbers

Broadcast mechanism
When calculating an array and a number , Apply this number to each element of the array , In fact, this number is expanded into the dimension of the sum array , Row number , An array with the same number of columns , Then do the operation on the corresponding element

Arrays and the calculation of arrays

identical shape Array of The calculation of , Directly add, subtract, multiply and divide the corresponding elements

Different shape Array of The calculation of , If it's two-dimensional , Rows and columns must have the same dimension , The other dimension is 1. If it is 3 One dimension minus one two dimension , Also look at rows and columns
It is also a broadcasting mechanism , It will expand the small one dimension of the row or column to the large one

example A two-dimensional

example The three dimensional