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Python Virtual Environments (or virtualenvs) are a mechanism to install Python packages not available system-wide, in user directories. They also allow you to have a different Python environment for each project, which is useful for example when you need different versions of the same package for different projects.
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A complete guide on virtualenvs can be found [here](https://docs.python.org/3/tutorial/venv.html). Next, we report only some basic commands.
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A complete guide on virtualenvs can be found [here](https://docs.python.org/3/tutorial/venv.html). Next, we report only some basic commands, with default options.
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#### Creating a Virtualenv
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Create a Python3 virtualenv in the folder `./pyenv` (done once per project):
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To create a Python3 virtualenv in the folder `./pyenv` type the following command:
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```
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python3 -m venv --system-site-packages ./pyenv
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```
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This must be done just once per project.
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Activate the virtualenv (done for each new shell from where you want to execute code belonging to the project):
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#### Activating a Virtualenv
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To ativate the virtualenv created above, type the following command:
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```
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source ./pyenv/bin/activate
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```
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This must be done for each new shell from where you want to execute code belonging to the project.
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#### Deactivating a Virtualenv
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Deactivate the virtualenv (the `deactivate` command is created when you activate your environment):
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To deactivate the virtualenv, type the following command:
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```
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deactivate
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```
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Note that the `deactivate` command is created when you activate the virtualenv.
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#### Installing Packages within a Virtualenv
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After activating a virtualenv, you can install new packages without special permissions using `pip` (guide [here](https://packaging.python.org/tutorials/installing-packages/#installing-from-pypi)). Those packages will be only available within that virtualenv.
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After activating a virtualenv, you can install new packages without special permissions using `pip`. You can find a guide on pip [here](https://packaging.python.org/tutorials/installing-packages/#installing-from-pypi). All packages installed within a virtualenv will be only available as long as it is active.
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