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python [2017/10/13 12:06]
bojar [Virtual environments] caveat about shebangs |
python [2023/02/14 11:13] (current)
jindra.helcl update |
| In this guide, I expect you are using Python3 (and ''pip3''), but (for old projects) you can use Python2 (and ''pip2'') as well. | In this guide, I expect you are using Python3 (and ''pip3''), but (for old projects) you can use Python2 (and ''pip2'') as well. |
| |
| * You can use the system Python (currently 2.7.6 and 3.4.3, in Ubuntu 14.04), but it is a bit old and will be changed when a new Ubuntu is installed at ÚFAL. | * You can use the system Python |
| * You can use any Python from ''/opt/python/'', e.g. for 3.6.3 add the following line to your .bashrc: <code>export PATH=/opt/python/3.6.3/bin:"${PATH}"</code> | * You can use any Python from ''/opt/python/'', e.g. for 3.11.0 add the following line to your .bashrc: <code>export PATH=/opt/python/3.11.0/bin:"${PATH}"</code> |
| * You can install modules with ''pip3''. If you are not using any [[#virtual environments]], you must add the ''-''''-user'' option, so it is installed in your home. In this case, don't forget the executable scripts are installed in ''~/.local/bin/'', so add the following line to your .bashrc: <code>export PATH=~/.local/bin:"${PATH}"</code> | * You can install modules with ''pip''. It is recommended to use [[#virtual environments]] for installing new packages. If you are not using virtual environments, you must add the ''-''''-user'' option, so it is installed in your home. In this case, don't forget the executable scripts are installed in ''~/.local/bin/'', so add the following line to your .bashrc: <code>export PATH=~/.local/bin:"${PATH}"</code> |
| * If you are using the system Python3 (3.4.3), note that it comes with a very old version of pip3 (1.5.4), so it is recommended to update it with <code>pip3 install --user --upgrade pip</code> | * Both the system Python3 and the Python3 from ''/opt/python/'' come with an old version of pip3, so it is recommended to update it with <code>pip3 install --user --upgrade pip</code> |
| * There are no UFAL-wide pre-installed Python modules. You need to install all modules you need yourself (with pip3). | * There are no UFAL-wide pre-installed Python modules. You need to install all modules you need yourself (with pip3). |
| |
| You can use [[https://docs.python.org/3/tutorial/venv.html|virtual environments]], e.g. one for each project (or a group of projects), so the version requirements of different projects do not collide. | You can use [[https://docs.python.org/3/tutorial/venv.html|virtual environments]], e.g. one for each project (or a group of projects), so the version requirements of different projects do not collide. |
| |
| Create a new virtual environment with | Create a new virtual environment with: |
| python3 -m venv my-project-name | python3 -m venv my-project-name |
| | or (for a specific version of python): |
| | /opt/python/$PYTHON_VERSION/bin/python3 -m venv my-project-name |
| | |
| where ''my-project-name'' can be a relative or absolute path to a directory which will be created. | where ''my-project-name'' can be a relative or absolute path to a directory which will be created. |
| **Caveat:** the path to the directory should be rather short, there is a limit on shebang paths so you can get strange errors like ''ipython3: bad interpreter: No such file or directory'' if your ipython3 installed in the venv starts with ''#!/...a..very..long..path...'' | **Caveat1:** the path to the directory should be rather short, there is a limit on shebang paths so you can get strange errors like ''ipython3: bad interpreter: No such file or directory'' if your ipython3 is installed in the venv starts with ''#!/..a..very..long..path..'' |
| | **Caveat2:** If ''my-project-name'' is a relative path, it will be concatenated with ''pwd -P'', i.e. with your actual directory with all symlinks resolved. If you want symlinks in the path, you must provide absolute path as ''my-project-name''. Note that e.g. ''/net/work/people'' is currently (2018-06) resolved by ''pwd -P'' to ''/lnet/.nfs/spec/work/people/'', but this path does not work on machines with native Lustre support.) |
| |
| You can use any Python version for the new environment, e.g. ''/opt/python/3.5.4/bin/python3 -m venv my-project-name-python3.5'' | You can use any Python version for the new environment, e.g. ''/opt/python/3.5.4/bin/python3 -m venv my-project-name-python3.5'' |
| virtualenv my-project-name | virtualenv my-project-name |
| source my-project-name/bin/activate | source my-project-name/bin/activate |
| | |
| | ==== IPython in virtual envs. ==== |
| | When using virtuaenvs, ipython is (in some versions) confused and uses an incorrect python interpreter. The following alias fixes this issue: |
| | <code> |
| | alias ipython="python -c 'import IPython; IPython.terminal.ipapp.launch_new_instance()'" |
| | </code> |
| |
| ===== Installing directly from Git ===== | ===== Installing directly from Git ===== |
