import numpy as np
a = np.array([[1, 3], [5, 7]])
a[:, 0] = 0
a[1, :] = 1
print(a.sum())

import numpy as np
a = np.arange(6).reshape(3, 2)
ia = np.array(((0, 0), (0, 1)))
ja = np.array(((1, 0), (0, 0)))
b = a[ia, ja]
print(b.sum() + b.ndim + b.size)

import numpy as np
a = np.array([3, 1, 2])
ia = np.array([True, False, True])
print(a[ia].sum())

import numpy as np
a = np.array([1, 2, 3])
ia = np.array([True >> 0, False, True])
print(a[ia].sum())

import numpy as np
vals = np.arange(1, 10)
bools = (vals % 2 == 0) | (vals % 3 == 0) & ~(vals % 9 == 0)
print(vals[bools])

import numpy as np
np.newaxis is None

import numpy as np
a = np.arange(4).reshape(2, 2)
b = a[:, np.newaxis, :]
print(b.shape)

import numpy as np
x = np.linspace(0, 2, 3)
y = np.linspace(0, 1, 2)
X, Y = np.meshgrid(x, y)
print(int(X.sum()), int(Y.sum()))

import numpy as np
x = np.linspace(0, 1, 2)
y = np.linspace(0, 1, 3)
X1, Y1 = np.meshgrid(x, y)
X2, Y2 = np.meshgrid(x, y, sparse=True)
print(*X1.shape, *Y1.shape, *X2.shape, *Y2.shape)