[FIXED] how to choose from a list based on sign changes in the list?

Issue

I have a list and inside of the list, the values and their signs are changing intermittently. I would like to define a function to extract from the list in every two consecutive sign-changing (Let's say zero-crossing points).

n = 5 #a number which comes from another list and here is written to make this example
List_1 = [-1.,-0.89, -0.77,-0.667, -0.55, -0.44,-0.333, -0.22, -0.111,0.,1,1.333,1.66,2,2.3,2.66,3.3, 3.667, 4,-30,-26.77,-23,-20.33-17.11,-13.8,-10,-7.44,-4.22, -1.,30,37.5,45,52.5,60]

def list_excluder:
   for i in range(n):
      zero_crossings = np.where(np.diff(np.sign(list_1[i])))[0]
      GG = list_1[i][zero_crossings[i-1]:zero_crossings[i]]
      ls.append(GG)

expected result:

ls = [[-1.,-0.89, -0.77,-0.667, -0.55, -0.44,-0.333, -0.22, -0.111,0.,1,1.333,1.66,2,2.3,2.66,3.3, 3.667, 4],[-30,-26.77,-23,-20.33-17.11,-13.8,-10,-7.44,-4.22, -1.,30,37.5,45,52.5,60.]]

Solution

I guess, here is your answer based on the explanation which was given by you:

def finding_bends(data, arr):
    zero_crossings = np.where(np.diff(np.sign(arr)))[0]
    zero_crossings = np.array(zero_crossings)
    BENDs = []
    
    for i in range(len(zero_crossings)-1):
#         print(i)
        BENDs.append(data[zero_crossings[i]:zero_crossings[i+1]])
        
    return BENDs

Answered By - john22