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# PyLammps and Jupyter Notebooks
This folder contains examples showcasing the usage of the PyLammps Python
interface and Jupyter notebooks. To use this you will need LAMMPS compiled as
a shared library and the LAMMPS Python package installed.
An extensive guide on how to achieve this is documented in the [LAMMPS manual](https://docs.lammps.org/Python_install.html). There is also a [PyLammps tutorial](https://docs.lammps.org/Howto_pylammps.html).
The following will show one way of creating a Python virtual environment
which has both LAMMPS and its Python package installed:
1. Clone the LAMMPS source code
```shell
$ git clone -b stable https://github.com/lammps/lammps.git
$ cd lammps
```
2. Create a build folder
```shell
$ mkdir build
$ cd build
```
3. Create a virtual environment for Python
```shell
$ python3 -m venv myenv
```
4. Extend `LD_LIBRARY_PATH` (Unix/Linux) or `DYLD_LIBRARY_PATH` (MacOS)
On Unix/Linux:
```shell
$ echo 'export LD_LIBRARY_PATH=$VIRTUAL_ENV/lib:$LD_LIBRARY_PATH' >> myenv/bin/activate
```
On MacOS:
```shell
echo 'export DYLD_LIBRARY_PATH=$VIRTUAL_ENV/lib:$DYLD_LIBRARY_PATH' >> myenv/bin/activate
```
5. Activate the virtual environment
```shell
$ source myenv/bin/activate
(myenv)$
```
6. Configure LAMMPS compilation (CMake)
```shell
(myenv)$ cmake -C ../cmake/presets/basic.cmake \
-D BUILD_SHARED_LIBS=on \
-D LAMMPS_EXCEPTIONS=on -D PKG_PYTHON=on \
-D CMAKE_INSTALL_PREFIX=$VIRTUAL_ENV \
../cmake
```
7. Compile LAMMPS
```shell
(myenv)$ cmake --build .
```
8. Install LAMMPS and Python package into virtual environment
```shell
(myenv)$ cmake --install .
```
9. Install other Python packages into virtual environment
```shell
(myenv)$ pip install jupyter matplotlib mpi4py
```
10. Navigate to pylammps examples folder
```shell
(myenv)$ cd ../python/examples/pylammmps
```
11. Launch Jupyter and work inside browser
```shell
(myenv)$ jupyter notebook
```
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