查找大型数组列表的特定索引

Question

I have a list of large array of different lengths. I want to find the position of each array larger than 420. For example, [size=(134,7),size=(620,7), size=(800,7),......]

My code is below

for x in x_train:
       if len(x)>420:
           print(x_train.index(x))

I got this error:

DeprecationWarning: elementwise == comparison failed; this will raise an 
error in the future.

What will be the correct solution?

Answer 1

That's a warning that something has been deprecated, but is not an error. I highly doubt your code block produced this warning, and chances are some imported library or other code was the cause.

Anyways, about your code, it is extremely inefficient, as once you find x you are looking for it again in the list. Use enumerate to get the index instead:

for i, x in enumerate(x_train):
    if len(x) > 420:
        print(i)

With a list comprehension, you can store all of the indexes:

indexes = [i for i, x in enumerate(x_train) if len(x) > 420]

Answer 2

Let's use List comprehension to solve it.

#Create a sample list of arrays of arbitrary length.
myList = [np.full((134,7), 10), np.full((620,7),0), np.full((800,7),0), np.full((150,7),0), np.full((500,7),0)]

indexes_gt_420 = [i for i in range(len(myList)) if len(myList[i]) > 420]
indexes_gt_420
     [1, 2, 4]