python - 如何有效地将 numpy ndarray 转换为元组列表？

Question

这是我得到的 numpy.ndarray:

a=[[[ 0.01, 0.02 ]], [[ 0.03, 0.04 ]]]

我想把它转换成

a = [(0.01, 0.02), (0.03, 0.04)]

目前我只是使用下面的for循环，但我不确定它是否足够高效:

b = []
for point in a:
   b.append((point[0][0], point[0][1]))
print(b)

我发现了一些 a similar question但是没有元组，所以建议的 ravel().tolist() 方法在这里对我不起作用。

Answer 1

# initial declaration
>>> a = np.array([[[ 0.01, 0.02 ]], [[ 0.03, 0.04 ]]])
>>> a
array([[[0.01, 0.02]],
       [[0.03, 0.04]]])

# check the shape
>>> a.shape
(2L, 1L, 2L)

# use resize() to change the shape (remove the 1L middle layer)
>>> a.resize((2, 2))
>>> a
array([[0.01, 0.02],
       [0.03, 0.04]])

# faster than a list comprehension (for large arrays)
# because numpy's backend is written in C

# if you need a vanilla Python list of tuples:
>>> list(map(tuple, a))
[(0.01, 0.02), (0.03, 0.04)]

# alternative one-liner:
>>> list(map(tuple, a.reshape((2, 2))))
...