# Error when calling device() **URL:** \ **Category:** PennyLane Help\ **Created:** [October 30, 2019, 9:32am UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259 "2019-10-30T09:32:24Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![abignu](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/abignu/32/142_2.png) [@abignu](https://discuss.pennylane.ai/u/abignu)\ **Post date:** [October 30, 2019, 9:32am UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/1 "2019-10-30T09:32:24Z")
Hi, I am having an error when calling the device: ``` DeviceError Traceback (most recent call last) in () 4 from pennylane.plugins import default_qubit 5 import matplotlib.pyplot as plt ----> 6 dev = qml.device('default.qubit', wires=1) 7 8 # Set a random seed /usr/local/lib/python3.6/dist-packages/pennylane/ __init__.py in device(name, *args, **kwargs) 128 129 raise DeviceError( --> 130 "Device does not exist. Make sure the required plugin is installed." 131 ) 132 DeviceError: Device does not exist. Make sure the required plugin is installed. ``` How can I solve it? Thanks in advance ---
**Author:** ![nathan](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/nathan/32/85_2.png) [@nathan](https://discuss.pennylane.ai/u/nathan)\ **Post date:** [October 30, 2019, 1:11pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/2 "2019-10-30T13:11:48Z")
Hi @abignu, 🤔 That’s an unusual error. The `default.qubit` plugin shouldn’t need any extra installation (comes pre-packaged within pennylane). My guess would be something has gone wrong with your pennylane install. Can you try the following and tell us the output? ```auto import pennylane as qml qml.about() ``` Also, can you try uninstalling and reinstalling it and let me know how that works? Thanks, Nathan PS you shouldn’t need to directly import the plugin (line 4 of your code). This is handled automatically by the `qml.device` function. ---
**Author:** ![abignu](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/abignu/32/142_2.png) [@abignu](https://discuss.pennylane.ai/u/abignu)\ **Post date:** [October 30, 2019, 2:15pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/3 "2019-10-30T14:15:23Z")
Hi @nathan, thanks for your reply. I was working in Google Colab. I found on another page that restarting the runtime fixes this issue. So I have already fixed it. Thanks for your time Agustin ---
**Author:** ![nathan](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/nathan/32/85_2.png) [@nathan](https://discuss.pennylane.ai/u/nathan)\ **Post date:** [October 30, 2019, 3:20pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/4 "2019-10-30T15:20:15Z")
Glad you got it working 🙂 ---
**Author:** ![fmacrae](https://avatars.discourse-cdn.com/v4/letter/f/67e7ee/32.png) [@fmacrae](https://discuss.pennylane.ai/u/fmacrae)\ **Post date:** [February 1, 2020, 4:14pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/5 "2020-02-01T16:14:29Z")
Hi both, I’m having the same error on colab and have tried restarting the runtime a couple of times without success. The output from qml.about() I get is: ```auto Version: 0.7.0 Summary: PennyLane is a Python quantum machine learning library by Xanadu Inc. Home-page: https://github.com/XanaduAI/pennylane Author: None Author-email: None License: Apache License 2.0 Location: /usr/local/lib/python3.6/dist-packages Requires: toml, networkx, numpy, autograd, appdirs, semantic-version, scipy Required-by: PennyLane-qiskit Platform info: Linux-4.14.137+-x86_64-with-Ubuntu-18.04-bionic Python version: 3.6.9 Numpy version: 1.17.5 Scipy version: 1.4.1 Installed devices: ``` This is what I’m doing to install it: [https://colab.research.google.com/drive/1bPipFzEuYgNPLVeJ5HXVP-kpG1o5QFmJ](https://colab.research.google.com/drive/1bPipFzEuYgNPLVeJ5HXVP-kpG1o5QFmJ) which I’m basing on [https://pennylane.ai/install.html](https://pennylane.ai/install.html) ---
**Author:** ![fmacrae](https://avatars.discourse-cdn.com/v4/letter/f/67e7ee/32.png) [@fmacrae](https://discuss.pennylane.ai/u/fmacrae)\ **Post date:** [February 1, 2020, 4:17pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/6 "2020-02-01T16:17:01Z")
Ignore me, restarted it again and it works 😊 ---
**Author:** ![Bayaniblues](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/bayaniblues/32/238_2.png) [@Bayaniblues](https://discuss.pennylane.ai/u/Bayaniblues)\ **Post date:** [March 2, 2020, 6:14pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/7 "2020-03-02T18:14:03Z")
I had the same problem with google collab, then I used this code snippet to restart runtime ``` import os def restart_runtime(): os.kill(os.getpid(), 9) restart_runtime() ``` Calling qml.about() should have the following output ``` Name: PennyLane Version: 0.8.1 Summary: PennyLane is a Python quantum machine learning library by Xanadu Inc. Home-page: https://github.com/XanaduAI/pennylane Author: None Author-email: None License: Apache License 2.0 Location: /usr/local/lib/python3.6/dist-packages Requires: appdirs, networkx, scipy, semantic-version, numpy, toml, autograd Required-by: Platform info: Linux-4.14.137+-x86_64-with-Ubuntu-18.04-bionic Python version: 3.6.9 Numpy version: 1.17.5 Scipy version: 1.4.1 Installed devices: - default.gaussian (PennyLane-0.8.1) - default.qubit (PennyLane-0.8.1) - default.tensor (PennyLane-0.8.1) - default.tensor.tf (PennyLane-0.8.1) ``` ---
**Author:** ![nathan](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/nathan/32/85_2.png) [@nathan](https://discuss.pennylane.ai/u/nathan)\ **Post date:** [March 2, 2020, 6:54pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/8 "2020-03-02T18:54:05Z")
If you’re working manually in a colab notebook, it should also be sufficient (and probably safer?) to restart the runtime via the available menu commands (i.e., no need to script it in python) ---
**Author:** ![angelinaG](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/angelinag/32/148_2.png) [@angelinaG](https://discuss.pennylane.ai/u/angelinaG)\ **Post date:** [June 20, 2020, 5:24pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/9 "2020-06-20T17:24:34Z")
Thank you so much! I faced a similar issue while working in Kaggle. Resolved after restarting the runtime environment with your code snippet. Only restarting the session didn’t quite help earlier. Thank you once again ---
**Author:** ![angelinaG](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/angelinag/32/148_2.png) [@angelinaG](https://discuss.pennylane.ai/u/angelinaG)\ **Post date:** [June 20, 2020, 5:25pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/10 "2020-06-20T17:25:37Z")
Very helpful. I had the similar output for qml.about() earlier but resolved after restarting the environment. ---
**Author:** ![angelinaG](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/angelinag/32/148_2.png) [@angelinaG](https://discuss.pennylane.ai/u/angelinaG)\ **Post date:** [June 20, 2020, 5:26pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/11 "2020-06-20T17:26:08Z")
Thank you for posting this query ---
**Author:** ![Vineesha](https://avatars.discourse-cdn.com/v4/letter/v/7ab992/32.png) [@Vineesha](https://discuss.pennylane.ai/u/Vineesha)\ **Post date:** [September 23, 2020, 5:09pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/12 "2020-09-23T17:09:28Z")
Hi, I am having an issue in loading the device default.tensor.tf on Pennylane 0.11.0. ``` dev = qml.device('default.tensor.tf', wires=4) ``` This gives the following error: ``` ImportError: default.tensor device requires TensorNetwork>=0.3 ``` This is the complete error message: ``` ModuleNotFoundError Traceback (most recent call last) C:\ProgramData\Anaconda3\envs\tf-gpu\lib\site- packages\pennylane\beta\devices\default_tensor.py in 26 try: ---> 27 import tensornetwork as tn 28 ModuleNotFoundError: No module named 'tensornetwork' During handling of the above exception, another exception occurred: ImportError Traceback (most recent call last) in ----> 1 dev = qml.device('default.tensor.tf', wires=4) C:\ProgramData\Anaconda3\envs\tf-gpu\lib\site- packages\pennylane\ __init__.py in device(name, *args, **kwargs) 182 183 # loads the plugin device class --> 184 plugin_device_class = plugin_devices[name].load() 185 186 if Version(version()) not in Spec(plugin_device_class.pennylane_requires): C:\ProgramData\Anaconda3\envs\tf-gpu\lib\site- packages\pkg_resources\ __init__.py in load(self, require, *args, **kwargs) 2448 if require: 2449 self.require(*args, **kwargs) -> 2450 return self.resolve() 2451 2452 def resolve(self): C:\ProgramData\Anaconda3\envs\tf-gpu\lib\site-packages\pkg_resources\ __init__.py in resolve(self) 2454 Resolve the entry point from its module and attrs. 2455 """ -> 2456 module = __import__ (self.module_name, fromlist=[' __name__'], level=0) 2457 try: 2458 return functools.reduce(getattr, self.attrs, module) C:\ProgramData\Anaconda3\envs\tf-gpu\lib\site-packages\pennylane\beta\devices\ __init__.py in 17 .. currentmodule:: pennylane.beta.devices 18 """ ---> 19 from .default_tensor import DefaultTensor 20 from .default_tensor_tf import DefaultTensorTF C:\ProgramData\Anaconda3\envs\tf-gpu\lib\site-packages\pennylane\beta\devices\default_tensor.py in 31 raise ImportError("default.tensor device requires TensorNetwork>=0.3") 32 except ImportError as e: ---> 33 raise ImportError("default.tensor device requires TensorNetwork>=0.3") 34 35 ImportError: default.tensor device requires TensorNetwork>=0.3 ``` The error persists even after upgrading my tensorflow version to 2.3.0 ``` import tensorflow as tf print(tf. __version__ ) 2.3.0 ``` How to resolve this? ---
**Author:** ![josh](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/josh/32/100_2.png) [@josh](https://discuss.pennylane.ai/u/josh)\ **Post date:** [September 23, 2020, 6:19pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/13 "2020-09-23T18:19:40Z")
HI @Vineesha! You will need to install [TensorNetwork](https://github.com/google/TensorNetwork) in order to use this device. You can do this via pip: ```auto pip install tensornetwork==0.3 ``` ---
**Author:** ![Vineesha](https://avatars.discourse-cdn.com/v4/letter/v/7ab992/32.png) [@Vineesha](https://discuss.pennylane.ai/u/Vineesha)\ **Post date:** [September 23, 2020, 6:39pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/14 "2020-09-23T18:39:18Z")
It works! Thank you 😃 ---
**Author:** ![Amandeep](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/amandeep/32/385_2.png) [@Amandeep](https://discuss.pennylane.ai/u/Amandeep)\ **Post date:** [October 16, 2020, 8:54am UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/15 "2020-10-16T08:54:38Z")
DeviceError: Device does not exist. Make sure the required plugin is installed. Please reply solution. Error is same ---
**Author:** ![josh](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/josh/32/100_2.png) [@josh](https://discuss.pennylane.ai/u/josh)\ **Post date:** [October 16, 2020, 9:54am UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/16 "2020-10-16T09:54:29Z")
Hi @Amandeep, what device are you using? - If you want to use a device from an external plugin, the plugin will need to be separately installed using `pip` before the device is available. - If you are using PennyLane with Google Colab, you will need to _restart the runtime_ (`Runtime` → `Restart Runtime`) before _any_ PennyLane devices are available. ---
**Author:** ![Amandeep](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/amandeep/32/385_2.png) [@Amandeep](https://discuss.pennylane.ai/u/Amandeep)\ **Post date:** [October 16, 2020, 10:23am UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/17 "2020-10-16T10:23:21Z")
device=qiskit.aer and i am not using google colab. ---
**Author:** ![josh](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/josh/32/100_2.png) [@josh](https://discuss.pennylane.ai/u/josh)\ **Post date:** [October 16, 2020, 4:24pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/18 "2020-10-16T16:24:29Z")
> device=qiskit.aer and i am not using google colab. To access the `qiskit.aer` device, you will need to install the [PennyLane-Qiskit plugin](https://pennylaneqiskit.readthedocs.io), if you haven’t already: ```python pip install pennylane-qiskit ``` If you _have_ installed the plugin already, then it could be something to do with your system configuration - could you post the output of `qml.about()`? ---
**Author:** ![Amandeep](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/amandeep/32/385_2.png) [@Amandeep](https://discuss.pennylane.ai/u/Amandeep)\ **Post date:** [October 17, 2020, 4:29am UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/19 "2020-10-17T04:29:35Z")
Name: PennyLane Version: 0.11.0 Summary: PennyLane is a Python quantum machine learning library by Xanadu Inc. Home-page: [https://github.com/XanaduAI/pennylane](https://github.com/XanaduAI/pennylane) Author: None Author-email: None License: Apache License 2.0 Location: c:\users\hp\anaconda3\lib\site-packages Requires: numpy, appdirs, scipy, autograd, toml, semantic-version, networkx Required-by: Platform info: Windows-10-10.0.19041-SP0 Python version: 3.8.3 Numpy version: 1.18.5 Scipy version: 1.5.0 Installed devices: - default.gaussian (PennyLane-0.11.0) - default.qubit (PennyLane-0.11.0) - default.qubit.autograd (PennyLane-0.11.0) - default.qubit.tf (PennyLane-0.11.0) - default.tensor (PennyLane-0.11.0) - default.tensor.tf (PennyLane-0.11.0) ---
**Author:** ![josh](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/josh/32/100_2.png) [@josh](https://discuss.pennylane.ai/u/josh)\ **Post date:** [October 18, 2020, 2:19pm UTC](https://discuss.pennylane.ai/t/error-when-calling-device/259/20 "2020-10-18T14:19:57Z")
@Amandeep it looks like the PennyLane-Qiskit plugin is not installed. You can install it using `pip`: ```auto pip install pennylane-qiskit ``` [Next page](https://discuss.pennylane.ai/t/error-when-calling-device/259.md?page=2)