import numpy as np
def fill(t):
for i in range(t.shape[1]):
temp_col = t[:,i]
nan_num = np.count_nonzero(temp_col!=temp_col)
if nan_num != 0:
temp_not_nan_col = temp_col[temp_col == temp_col]
temp_col[np.isnan(temp_col)] = temp_not_nan_col.mean()
return t
t = np.arange(24).reshape((4,6)).astype("float")
t[1,2:] = np.nan
print(t)
t=fill(t)
print(t)