# Pip Install Optional Dependency

Sometimes, the users may not need to install all dependencies of a package, since they will not use the part of it.

We can assign some optional dependencies for a python package.

# How

## `setup.py`

Add the *extras\_require* parameter in the setup function.

```python
setup(  
    # ...  
    extras_require={  
        'plotter': ['matplotlib'],  
        'full': ['matplotlib', 'tensorflow'],  
    },  
}
```

## Command Line

```bash
pip install package_name  
pip install package_name[plotter] # Install matplotlib  
pip install package_name[full] # Install matplotlib, tensorflow
```

# CVNN

Take CVNN, a python package, as an example:

## Document

By its document, we can install minimum dependencies:

```bash
pip install cvnn
```

It also provides plotting functions:

```bash
pip install cvnn[plotter]
```

## Source Code

In python source codes, the package put import part into a try block:

```python
try:  
    import plotly  
    import plotly.graph_objects as go  
    import plotly.figure_factory as ff  
    AVAILABLE_LIBRARIES.add('plotly')  
except ImportError as e:  
    logger.info("Plotly not installed,...")
```

# Reference

*   [https://github.com/NEGU93/cvnn](https://github.com/NEGU93/cvnn)
*   [https://stackoverflow.com/questions/6237946/optional-dependencies-in-distutils-pip](https://stackoverflow.com/questions/6237946/optional-dependencies-in-distutils-pip)
*   [https://stackoverflow.com/questions/1471994/what-is-setup-py](https://stackoverflow.com/questions/1471994/what-is-setup-py)