a = array([[1, 2], [3, 4]])

a.size

a.shape

a.dtype

a.itemsize

a.nbytes

a.strides

array(a, order='F').strides

a = rand(1000, 1000)

timeit -n 100 b1 = a.flatten()

timeit -n 100 b2 = a.ravel()

array_equal(a.flatten(), a.ravel())

b1 = a.flatten()
b2 = a.ravel()
# return the address of the memory block
id = lambda x: x.__array_interface__['data'][0]
print(id(a), id(b1), id(b2))

b = zeros(1000000)

timeit -n 100 b[:] = a.ravel()

timeit -n 100 b[:] = a.T.ravel()

timeit -n 100 b[:] = a.ravel(order='F')

a = rand(10000, 1000)
b = arange(10000)

c = a + b

timeit -n 10 c = a + tile(b.reshape((-1, 1)), (1, 1000))

timeit -n 10 c = a + b.reshape((-1, 1))

array_equal(a + tile(b.reshape((-1, 1)), (1, 1000)), a + b.reshape((-1, 1)))

a = rand(10000, 100)
ind = randint(low=0, high=10000, size=10000)

timeit -n 100 b = a[ind,:]

timeit -n 100 b = take(a, ind, axis=0)

array_equal(a[ind,:], take(a, ind, axis=0))

ind = a[:,0] > .5

timeit -n 10 b = a[ind,:]

timeit -n 10 b = compress(ind, a, axis=0)

array_equal(a[ind,:], compress(ind, a, axis=0))

def loadtxt_fast(filename, dtype=int32, skiprows=0, delimiter=' '):
    def iter_func():
        with open(filename, 'r') as infile:
            for _ in range(skiprows):
                next(infile)
            skip = 0
            for line in infile:
                line = line.rstrip().split(delimiter)
                for item in line:
                    yield dtype(item)
            loadtxt_fast.rowlength = len(line)
    data = np.fromiter(iter_func(), dtype=dtype)
    data = data.reshape((-1, loadtxt_fast.rowlength))
    return data

a = randint(low=0, high=1000, size=(100000, 10))
fn = '_array.txt'
savetxt(fn, a, fmt='%d')

timeit -n 1 b = loadtxt(fn)

timeit -n 1 b = loadtxt_fast(fn)

array_equal(loadtxt(fn), loadtxt_fast(fn))

a = rand(1000000)

timeit -n 10 max(a)

timeit -n 10 a.max()

max(a) == a.max()