type hinting default values in classes

user_12894878 0
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How do I properly create type hints if the value isn't assigned yet.

For example:

class foo():
    def __init__():
        data: np.ndarray = None

    def load_data():
        data = np.loadtxt(...)

Now I obviously get a warning, that type ndarray is expected, and not None. What is an elegant solution to this? Do I just make up some ndarray like data: np.ndarray = np.array([])? That seams just wrong to me, and I'm sure there is a better way of doing it.

I still prefer the None version, because if there is an error with reading the numpy array, I will get an error like "can't calculate ... with type None". Then I imideatly know, it didn't read the file. Whereas, if the array is just empty, I might get weird errors, I don't understand.

SOLUTION:

Thanks to the commentators, pointing this out. The solution is importing Optional from typing, and then use Optional[np.ndarray] instead of np.ndarray

typing numpy class python
1 Answers

Consider using data: np.ndarray = np.empty([])
Or if you know the dimension of the array, initialize it with its dimensions.
See numpy.empty for more information.

Good Luck,
Ben

user_88568000
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