我如何在python中创建一个数组，其元素为2个数组

Question

I am doing a classification problem. My training set is X_train containing 60000 elements and each element has 784 features (basically the intensity of pixels of an image). I want to reshape the images in a 28 * 28 array and store them in another array. I tried but can't find a solution. How can I do that?

for x in range(60000):
    X_new=X_train[x].reshape(28,28)

len(X_new)

I expect len(X_new) be 60000 but its length is showing as 28.

Answer 1

Without context, both other answers might be right. However, I'm going to venture a guess that your X_train is already a numpy.array with shape (60000, 784) . In this case len(X_train) will return 60000 . If so, what you want to do is simply:

X_new = X_train.reshape((-1, 28, 28))

Answer 2

You should assign X_train[x] instead of X_new :

for x in range(60000): X_train[x] = X_train[x].reshape(28,28)

otherwise, X_new will store only the last element of the list. You can create a new array if you do not want to spoil the old one:

X_new = [X_train[x].reshape(28,28) for x in range(60000)]

Answer 3

Possibly you mean to do this:

X_new = []
for x in range(60000):
    X_new.append(X_train[x].reshape(28, 28))

len(X_new)

You can also use a list comprehension

X_new = [x.reshape(28, 28) for x in X_train]