tox unable to find boto3 even though it is installed

I have a Python tox project where I run the tox for running the test case and I came across one error a few hours back and am unable to resolve it till now. My module is using boto3 library and is installed using both the commands:

pip3 install boto3  

pip install boto3 //for venv environments

When I try to install it again it gives me the below stack trace:

Requirement already satisfied: boto3 in ./venv/lib/python3.8/site-packages (1.26.34)
Requirement already satisfied: botocore<1.30.0,>=1.29.34 in ./venv/lib/python3.8/site-packages (from boto3) (1.29.34)
Requirement already satisfied: jmespath<2.0.0,>=0.7.1 in ./venv/lib/python3.8/site-packages (from boto3) (1.0.1)
Requirement already satisfied: s3transfer<0.7.0,>=0.6.0 in ./venv/lib/python3.8/site-packages (from boto3) (0.6.0)
Requirement already satisfied: urllib3<1.27,>=1.25.4 in ./venv/lib/python3.8/site-packages (from botocore<1.30.0,>=1.29.34->boto3) (1.26.13)
Requirement already satisfied: python-dateutil<3.0.0,>=2.1 in ./venv/lib/python3.8/site-packages (from botocore<1.30.0,>=1.29.34->boto3) (2.8.2)
Requirement already satisfied: six>=1.5 in ./venv/lib/python3.8/site-packages (from python-dateutil<3.0.0,>=2.1->botocore<1.30.0,>=1.29.34->boto3) (1.16.0)

But when I run tox it gives me the below error:

 File "/Users/tony/IdeaProjects/abc/provisioner/.tox/py38/lib/python3.8/site-packages/api/lambda_handler.py", line 1, in <module>
    import boto3
ModuleNotFoundError: No module named 'boto3'

Is there some path issue? I am using Python 3.8.10. I tried uninstalling and installing the packages but nothing changed.

Any help is much appreciated.

Solution

tox creates an isolated environment for building and testing. So, when you install a package somewhere, here boto3 with pip/pip3, maybe system-wide, tox ignores that - and that is a good thing, otherwise it would be impossible to have a clean test environment.

You need to provide the necessary dependencies to tox.

tox automatically installs a package, ie. when there is a setup.py or a pyproject.toml. You could also provide your dependencies directly via the deps configuration key:

[testenv]
commands = ...
deps = boto3

There is another way. You could "break" the test isolation by using the tox-current-env plugin, see https://pypi.org/project/tox-current-env/

Disclaimer

I am on of the tox maintainers.