Numpy array examples

>>> import numpy as np
>>> ax = np.array([1,2,3,4])
>>> ax
array([1, 2, 3, 4])
>>> ax * 2
array([2, 4, 6, 8])
>>> ay = np.array([5, 6, 7, 8])
>>> ax + 10
array([11, 12, 13, 14])
>>> ax + ay
array([ 6,  8, 10, 12])
>>> ax * ay
array([ 5, 12, 21, 32])
>>> grid = np.zeros(shape=(10000,10000), dtype=float)
>>> grid
array([[ 0.,  0.,  0., ...,  0.,  0.,  0.],
       [ 0.,  0.,  0., ...,  0.,  0.,  0.],
       [ 0.,  0.,  0., ...,  0.,  0.,  0.],
       ...,
       [ 0.,  0.,  0., ...,  0.,  0.,  0.],
       [ 0.,  0.,  0., ...,  0.,  0.,  0.],
       [ 0.,  0.,  0., ...,  0.,  0.,  0.]])
>>> grid += 10
>>> grid
array([[ 10.,  10.,  10., ...,  10.,  10.,  10.],
       [ 10.,  10.,  10., ...,  10.,  10.,  10.],
       [ 10.,  10.,  10., ...,  10.,  10.,  10.],
       ...,
       [ 10.,  10.,  10., ...,  10.,  10.,  10.],
       [ 10.,  10.,  10., ...,  10.,  10.,  10.],
       [ 10.,  10.,  10., ...,  10.,  10.,  10.]])
>>> np.sin(grid)
array([[-0.54402111, -0.54402111, -0.54402111, ..., -0.54402111,
        -0.54402111, -0.54402111],
       [-0.54402111, -0.54402111, -0.54402111, ..., -0.54402111,
        -0.54402111, -0.54402111],
       [-0.54402111, -0.54402111, -0.54402111, ..., -0.54402111,
        -0.54402111, -0.54402111],
       ...,
       [-0.54402111, -0.54402111, -0.54402111, ..., -0.54402111,
        -0.54402111, -0.54402111],
       [-0.54402111, -0.54402111, -0.54402111, ..., -0.54402111,
        -0.54402111, -0.54402111],
       [-0.54402111, -0.54402111, -0.54402111, ..., -0.54402111,
        -0.54402111, -0.54402111]])
>>> np.sqrt(ax)
array([ 1.        ,  1.41421356,  1.73205081,  2.        ])
>>> np.cos(ax)
array([ 0.54030231, -0.41614684, -0.9899925 , -0.65364362])
>>> a = np.array([1,2,3,4], [5, 6, 7, 8], [9,10,11,12])
Traceback (most recent call last):
  File "", line 1, in
ValueError: only 2 non-keyword arguments accepted
>>> a = np.array([[1,2,3,4], [5, 6, 7, 8], [9,10,11,12]])
>>> a
array([[ 1,  2,  3,  4],
       [ 5,  6,  7,  8],
       [ 9, 10, 11, 12]])
>>> # select row 1
...
>>> a[1]
array([5, 6, 7, 8])
>>> # select column 1
...
>>> a[:1]
array([[1, 2, 3, 4]])
>>> a[:,1]
array([ 2,  6, 10])
>>> # select sub region and change it
...
>>> a[1:3, 1:3]
array([[ 6,  7],
       [10, 11]])
>>> a[1:3, 1:3] += 10
>>> a
array([[ 1,  2,  3,  4],
       [ 5, 16, 17,  8],
       [ 9, 20, 21, 12]])
>>> a + [100, 101,102,103]
array([[101, 103, 105, 107],
       [105, 117, 119, 111],
       [109, 121, 123, 115]])
>>> a
array([[ 1,  2,  3,  4],
       [ 5, 16, 17,  8],
       [ 9, 20, 21, 12]])
>>> np.where(a<10 10="" a="" br="">array([[ 1,  2,  3,  4],
       [ 5, 10, 10,  8],
       [ 9, 10, 10, 10]])
>>> a
array([[ 1,  2,  3,  4],
       [ 5, 16, 17,  8],
       [ 9, 20, 21, 12]])