Python Appending a dictionary whose keys contain np arrays

[member 428835]

Hi PF!

I have a large dataset called data_dict I'm parsing that's stored as a numpy array. I'm subcategorizing it via a dictionary titled data_dict. Currently there is a dictionary key called key_curr that stores an np array data_col_prev. I'd like to append to this key data_col_curr. When I execute the following:

data_dict.setdefault(key_curr, []).np.append(data_col_curr)

I receive the error
>> AttributeError: 'numpy.ndarray' object has no attribute 'np'

When I execute

data_dict.setdefault(key_curr, []).append(data_col_curr)

I receive the error
>> AttributeError: 'numpy.ndarray' object has no attribute 'append'

Any help would be awesome!

 

[PeterDonis]

It seems like you are saying that executing the same statement gives you two different errors. That doesn't make sense.

That said, I don't understand why the "np" is in the statement you are executing. I also don't understand why the default value in the "setdefault" call is a Python list, but you say the values stored in the dict are np arrays.

 

[member 428835]

It seems like you are saying that executing the same statement gives you two different errors. That doesn't make sense.

That said, I don't understand why the "np" is in the statement you are executing. I also don't understand why the default value in the "setdefault" call is a Python list, but you say the values stored in the dict are np arrays.

Sorry, I changed the second line of code, which I now think makes more since. And sorry, np comes from the beginnning of the python file: import numpy as np

 

[member 428835]

It seems like you are saying that executing the same statement gives you two different errors. That doesn't make sense.

That said, I don't understand why the "np" is in the statement you are executing. I also don't understand why the default value in the "setdefault" call is a Python list, but you say the values stored in the dict are np arrays.

Actually, your comment regarding the [] not compatible with numpy led to me getting a solution (I changed the np array to standard array via np_data.tolist() )

Thanks!

 

[PeterDonis]

I changed the second line of code

Yes, I see that.

np comes from the beginnning of the python file: import numpy as np

That doesn't make "np" an attribute of arrays. So that explains the error you are getting from the first line of code.

I changed the np array to standard array via np_data.tolist()

Actually it's a Python list object, not a Python array object. Python array objects are different.

As long as you don't need any of the capabilities of the np array object, this should work fine.