为什么这个 Python 数组不切片？

Question

Initial data is:

array([[0.0417634 ],
   [0.04493844],
   [0.04932728],
   [0.04601787],
   [0.04511007],
   [0.04312284],
   [0.0451733 ],
   [0.04560687],
   [0.04263394],
   [0.04183227],
   [0.048634  ],
   [0.05198746],
   [0.05615724],
   [0.05787913], dtype=float32)

then i transformed it in 2d array

array2d = np.reshape(dataset, (-1, 2))

now i have

array([[0.0417634 , 0.04493844],
   [0.04932728, 0.04601787],
   [0.04511007, 0.04312284],
   [0.0451733 , 0.04560687],
   [0.04263394, 0.04183227],
   [0.048634  , 0.05198746],
   [0.05615724, 0.05787913],
   [0.05989346, 0.0605077 ], dtype=float32)

Now i'm going to calcolulate the mean between each element of the array

paa = []
paa.append(array2d.mean(axis=1))

now i want a list of intervals from this list

intervals = paa[::10]
intervals

but the result is the same list (paa). Why? Already tried to convert it in np.array(paa)

Expected a new list with less elements. Since 10 is the nr of steps i'm expecting [0.0417634, ... paa[11], .... paa[21] .... ]

Answer 1

np.mean will return a np.array . You are taking the result and appending it into a list . When you are slicing it, you're getting the 0th (and only) element in paa , which is an entire np.array .

Get rid of the list and append and slice directly into the result of mean.