# TypeError: cannot pickle 'sqlite3.Connection' object when running Ray Tune with Jupyter notebook script

**URL:** <https://brian.discourse.group/t/typeerror-cannot-pickle-sqlite3-connection-object-when-running-ray-tune-with-jupyter-notebook-script/835>\
**Category:** Support\
**Tags:** parallel\
**Created:** [17 November 2022 17:26 UTC](https://brian.discourse.group/t/typeerror-cannot-pickle-sqlite3-connection-object-when-running-ray-tune-with-jupyter-notebook-script/835 "2022-11-17T17:26:46Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![DavidKing2020](https://avatars.discourse-cdn.com/v4/letter/d/e0b2c6/32.png) [@DavidKing2020](https://brian.discourse.group/u/DavidKing2020)\
**Post date:** [17 November 2022 17:26 UTC](https://brian.discourse.group/t/typeerror-cannot-pickle-sqlite3-connection-object-when-running-ray-tune-with-jupyter-notebook-script/835/1 "2022-11-17T17:26:47Z")

</div>

# Description of problem

I got an “TypeError: cannot pickle ‘sqlite3.Connection’ object” error when running the attached Ray Tune code. The code need to import a notebook script called ttt.ipynb. Such an error won’t show up if using a python script instead.

# Minimal code to reproduce problem

[example.py](https://brian.discourse.group/uploads/short-url/5gcBrUZNDYkHY9WWnjRCvnAP5PV.py) (936 Bytes)

The ttt.ipynb is as follows:

```
  from brian2 import *

 def ttt():
     set_device('runtime')
     prefs.codegen.target = 'numpy'
     return 2.0

```

# Full traceback of error (if relevant)

```
  PC:wxie:ray.tune>ipython example.py
  ---------------------------------------------------------------------------
  TypeError Traceback (most recent call last)
  File ~/code_example/python/ray.tune/example.py:24, in <module>
       20 raw_log_name = "example"
       22 algorithm = HyperOptSearch(search_space, metric="SCORE", mode="max", n_initial_points=1)
  ---> 24 tuner = tune.Tuner(objective,
       25 tune_config = tune.TuneConfig(
       26 num_samples = 1,
       27 search_alg=algorithm,
       28 ),
       29 param_space=search_space,
       30 run_config = air.RunConfig(local_dir = raw_log_dir, name = raw_log_name)
       31 )
       33 results = tuner.fit()
       34 print(results.get_best_result(metric="SCORE", mode="max").config)

  File ~/anaconda3/envs/b2c/lib/python3.8/site-packages/ray/tune/tuner.py:152, in Tuner. __init__ (self, trainable, param_space, tune_config, run_config, _tuner_kwargs, _tuner_internal)
      150 kwargs.pop(_SELF, None)
      151 if not self._is_ray_client:
  --> 152 self._local_tuner = TunerInternal(**kwargs)
      153 else:
      154 self._remote_tuner = _force_on_current_node(
      155 ray.remote(num_cpus=0)(TunerInternal)
      156 ).remote(**kwargs)

  File ~/anaconda3/envs/b2c/lib/python3.8/site-packages/ray/tune/impl/tuner_internal.py:125, in TunerInternal. __init__ (self, restore_path, resume_config, trainable, param_space, tune_config, run_config, _tuner_kwargs)
      122 pickle.dump(self, fp)
      124 with open(experiment_checkpoint_path / _TRAINABLE_PKL, "wb") as fp:
  --> 125 pickle.dump(self._trainable, fp)
      126 self._maybe_warn_resource_contention()

  File ~/anaconda3/envs/b2c/lib/python3.8/site-packages/ray/cloudpickle/cloudpickle_fast.py:55, in dump(obj, file, protocol, buffer_callback)
       45 def dump(obj, file, protocol=None, buffer_callback=None):
       46 """Serialize obj as bytes streamed into file
       47
       48 protocol defaults to cloudpickle.DEFAULT_PROTOCOL which is an alias to
     (...)
       53 compatibility with older versions of Python.
       54 """
  ---> 55 CloudPickler(
       56 file, protocol=protocol, buffer_callback=buffer_callback
       57 ).dump(obj)

  File ~/anaconda3/envs/b2c/lib/python3.8/site-packages/ray/cloudpickle/cloudpickle_fast.py:627, in CloudPickler.dump(self, obj)
      625 def dump(self, obj):
      626 try:
  --> 627 return Pickler.dump(self, obj)
      628 except RuntimeError as e:
      629 if "recursion" in e.args[0]:

  TypeError: cannot pickle 'sqlite3.Connection' object

```

---

<div class="post-metadata">

**Author:** ![mstimberg](https://yyz2.discourse-cdn.com/free1/user_avatar/brian.discourse.group/mstimberg/32/11_2.png) [@mstimberg](https://brian.discourse.group/u/mstimberg)\
**Post date:** [17 November 2022 20:52 UTC](https://brian.discourse.group/t/typeerror-cannot-pickle-sqlite3-connection-object-when-running-ray-tune-with-jupyter-notebook-script/835/2 "2022-11-17T20:52:07Z")

</div>

Hi, I had a quick look and was able to reproduce the error. Running notebooks from another process can be a bit fragile, in particular when code then runs things in separate parallel processes. I think the issue here is simply that your notebook uses `from brian2 import *`, which imports a lot of things into the namespace and then leads to name clashes. Try importing `brian2` by name instead, e.g. like this

```python
import brian2

def ttt():
    brian2.set_device('runtime')
    brian2.prefs.codegen.target = 'numpy'
    return 2.0

```

or, for slightly less typing:

```python
import brian2 as b2
def ttt():
    b2.set_device('runtime')
    b2.prefs.codegen.target = 'numpy'
    return 2.0

```

In your small example, this is enough to make it work for me. Hope it works for your more complex code as well!