Error: 'DefaultQubit' object has no attribute 'num_wires'

[nireekreddy]

Node number

Codercise I.12.1.

Expected behavior

Compile without error

Actual behavior

Error: 'DefaultQubit' object has no attribute 'num_wires'

Additional information

No response

Source code

bits = [int(x) for x in np.binary_repr(basis_id, width=dev.num_wires)]

Tracebacks

No response

Check other issues

• I have searched existing GitHub issues to make sure the issue does not already exist.

[isaacdevlugt]

Hey @nireekreddy! Thanks 👍. The num_wires attribute was removed with the new device API changes (v0.33 I believe). You can do this instead:

num_wires = len(dev.wires)
bits = [int(x) for x in np.binary_repr(basis_id, width=num_wires)]

Let me know if that works!

[nireekreddy]

@isaacdevlugt , thanks for the prompt reply. It works. Could you also change it in the codebook ? So that someone else trying to learn will not waste time on it the simple error. This was the main reason I opened an issue here. thanks :)

[isaacdevlugt]

Ah! Yes I will fix that 😄.

[MadhurimaNayak]

@isaacdevlugt hey! I tried this node yesterday and this issue wasn't fixed.

[isaacdevlugt]

Hey @MadhurimaNayak, apologies! I merged that PR. You can still use this fix as a temporary workaround:

num_wires = len(dev.wires)
bits = [int(x) for x in np.binary_repr(basis_id, width=num_wires)]

[lionelbrits]

@isaacdevlugt This is still outstanding :)

[isaacdevlugt]

Hey @lionelbrits, what's the code you're trying to run?

[lionelbrits]

@isaacdevlugt Codercise I.12.1

[isaacdevlugt]

I just want to make sure that we're talking about the same code here. Do you mind copy-pasting what you're trying to run on the codebook website?

[lionelbrits]

@isaacdevlugt:
This is the same bug that is discussed here. When the exercise loads the code contains

    bits = [int(x) for x in np.binary_repr(basis_id, width=dev.num_wires)]

which needs to be changed to

    bits = [int(x) for x in np.binary_repr(basis_id, width=num_wires)]

in order to run. As I have completed the exercise, pasting my version wouldn't really help here.
tl;rd: Codercise I.12.1 loads referencing dev.num_wires which is deprecated.

[isaacdevlugt]

Thanks! Indeed, dev.num_wires is still there. It must've been my browser cache misleading me 😅.

We can address issues that crop up on codebook.xanadu.ai in terms of helping you achieve the correct answers that it expects, but changing the source code at this juncture is not something we're doing because we're migrating the codebook to https://pennylane.ai/codebook/ 🚀! Please visit that URL for the most up-to-date and maintained version of the codebook