The reshape(rows, columns) command rearranges an array.

ravel() flattens an array into one dimension.

resize(rows, columns) works like reshape, but in place.

A dimension specified as -1 is automatically calculated.

concatenate() is the general form.

vstack() and hstack() work on particular axis.

column_stack() is a specialization of vstack() for making many 1D arrays into columns of a 2D array.

array_split() is the general form.

hsplit(), vsplit() work on particular axis

Create 1D using array([1, 2, 3]).

Create 2D using array([[1, 2], [3, 4]]).

Or zeros(num_rows, num_columns). random.randn(num_rows, num_columns) produces a random array of a given shape.

fromfunction(f, shape) calls a function repeatedly as f(x, y, z, …):

• shape is a tuple of integers determining the dimensions
• if f returns something other than a scalar, that will interact with shape to make some other weird shape

arange(min, max, step) returns an array range. linspace(min, max, num_elements) does the same.

eye() makes an identity array (1s on the diagonal, zeroes elsewhere).

The view() method makes a copy. Slicing (by index) triggers this.

copy() is a deep copy.

If arrays have different rank, the small array has 1 preprended to its shape until they match.

If array A has a dimension of 1, and array B does not, the value from A will be repeated across that dimension..