Numpy: Fix array with rows of different lengths by filling the empty elements with zeros

This could be one approach -

def numpy_fillna(data):    # Get lengths of each row of data    lens = np.array([len(i) for i in data])    # Mask of valid places in each row    mask = np.arange(lens.max()) < lens[:,None]    # Setup output array and put elements from data into masked positions    out = np.zeros(mask.shape, dtype=data.dtype)    out[mask] = np.concatenate(data)    return out

Sample input, output -

In [222]: # Input object dtype array     ...: data = np.array([[1, 2, 3, 4],     ...:                  [2, 3, 1],     ...:                  [5, 5, 5, 5, 8 ,9 ,5],     ...:                  [1, 1]])In [223]: numpy_fillna(data)Out[223]: array([[1, 2, 3, 4, 0, 0, 0],       [2, 3, 1, 0, 0, 0, 0],       [5, 5, 5, 5, 8, 9, 5],       [1, 1, 0, 0, 0, 0, 0]], dtype=object)

You could use pandas instead of numpy:

In [1]: import pandas as pdIn [2]: df = pd.DataFrame([[1, 2, 3, 4],   ...:                    [2, 3, 1],   ...:                    [5, 5, 5, 5],   ...:                    [1, 1]], dtype=float)In [3]: df.fillna(0.0).valuesOut[3]: array([[ 1.,  2.,  3.,  4.],       [ 2.,  3.,  1.,  0.],       [ 5.,  5.,  5.,  5.],       [ 1.,  1.,  0.,  0.]])

use np.pad().

In [62]: arrOut[62]: [array([0]), array([83, 74]), array([87, 61, 23]), array([71,  3, 81, 77]), array([20, 44, 20, 53, 60]), array([54, 36, 74, 35, 49, 54]), array([11, 36,  0, 98, 29, 87, 21]), array([ 1, 22, 62, 51, 45, 40, 36, 86]), array([ 7, 22, 83, 58, 43, 59, 45, 81, 92]), array([68, 78, 70, 67, 77, 64, 58, 88, 13, 56])]In [63]: max_len = np.max([len(a) for a in arr])In [64]: np.asarray([np.pad(a, (0, max_len - len(a)), 'constant', constant_values=0) for a in arr])Out[64]: array([[ 0,  0,  0,  0,  0,  0,  0,  0,  0,  0],       [83, 74,  0,  0,  0,  0,  0,  0,  0,  0],       [87, 61, 23,  0,  0,  0,  0,  0,  0,  0],       [71,  3, 81, 77,  0,  0,  0,  0,  0,  0],       [20, 44, 20, 53, 60,  0,  0,  0,  0,  0],       [54, 36, 74, 35, 49, 54,  0,  0,  0,  0],       [11, 36,  0, 98, 29, 87, 21,  0,  0,  0],       [ 1, 22, 62, 51, 45, 40, 36, 86,  0,  0],       [ 7, 22, 83, 58, 43, 59, 45, 81, 92,  0],       [68, 78, 70, 67, 77, 64, 58, 88, 13, 56]])