If I initialise a python list
x = [[],[],[]]
print(x)
then it returns
[[], [], []]
but if I do the same with a numpy array
x = np.array([np.array([]),np.array([]),np.array([])])
print(x)
then it only returns
[]
How can I make it return a nested empty list as it does for a normal python list?
It actually does return a nested empty list. For example, try
x = np.array([np.array([]),np.array([]),np.array([])])
>>> array([], shape=(3, 0), dtype=float64)
or
>>> print x.shape
(3, 0)
Don't let the output of print x fool you. These types of outputs merely reflect the (aesthetic) choices of the implementors of __str__ and __repr__. To actually see the exact dimension, you need to use things like .shape.
To return a nested empty list from a numpy array, you can do:
x.tolist()
[[], [], []]
However, even if it prints only [], the shape is correct:
x.shape
(3, 0)
And you can access any element like a list:
x[0]
array([], dtype=float64)
tolist is a clever idea here.The easiest solution for you is to convert it to a list with tolist
x = np.array([np.array([]),np.array([]),np.array([])])
print(x)
[]
print(x.tolist())
[[], [], []]
tolist is a clever idea here.