# Contributing to GeoPandas

(Contribution guidelines largely copied from pandas)

## Overview

Contributions to GeoPandas are very welcome. They are likely to be accepted more quickly if they follow these guidelines.

At this stage of GeoPandas development, the priorities are to define a simple, usable, and stable API and to have clean, maintainable, readable code. Performance matters, but not at the expense of those goals.

In general, GeoPandas follows the conventions of the pandas project where applicable.

In particular, when submitting a pull request:

- All existing tests should pass. Please make sure that the test suite passes, both locally and on Travis CI. Status on Travis will be visible on a pull request. If you want to enable Travis CI on your own fork, please read the pandas guidelines link above or the getting started docs.
- New functionality should include tests. Please write reasonable tests for your code and make sure that they pass on your pull request.
- Classes, methods, functions, etc. should have docstrings. The first line of a docstring should be a standalone summary. Parameters and return values should be ducumented explicitly.
- GeoPandas supports python 2 (2.6+) and python 3 (3.2+) with a single code base. Use modern python idioms when possible that are compatibile with both major versions, and use the six library where helpful to smooth over the differences. Use `from __future__ import` statements where appropriate. Test code locally in both python 2 and python 3 when possible (all supported versions will be automatically tested on Travis CI).
- Follow PEP 8 when possible.
- Imports should be grouped with standard library imports first, 3rd-party libraries next, and geopandas imports third. Within each grouping, imports should be alphabetized. Always use absolute imports when possible, and explicit relative imports for local imports when necessary in tests.

### Seven Steps for Contributing

There are seven basic steps to contributing to geopandas:

1. Fork the geopandas git repository
2. Create a development environment
3. Install geopandas dependencies
4. Make a `development` build of geopandas
5. Make changes to code and add tests
6. Update the documentation
7. Submit a Pull Request

Each of these 7 steps is detailed below.

## 1) Forking the geopandas repository using Git

To the new user, working with Git is one of the more daunting aspects of contributing to geopandas*. It can very quickly become overwhelming, but sticking to the guidelines below will help keep the process straightforward and mostly trouble free. As always, if you are having difficulties please feel free to ask for help.

The code is hosted on GitHub. To contribute you will need to sign up for a free GitHub account. We use Git for version control to allow many people to work together on the project.

Some great resources for learning Git:

- Software Carpentry’s Git Tutorial
- Atlassian
- the GitHub help pages.
- Matthew Brett’s Pydagogue.

### Getting started with Git

GitHub has instructions for installing git, setting up your SSH key, and configuring git. All these steps need to be completed before you can work seamlessly between your local repository and GitHub.

### Forking

You will need your own fork to work on the code. Go to the geopandas project page and hit the `Fork` button. You will want to clone your fork to your machine:

    git clone git@github.com:your-user-name/geopandas.git geopandas-yourname
    cd geopandas-yourname
    git remote add upstream git://github.com/geopandas/geopandas.git

This creates the directory geopandas-yourname and connects your repository to the upstream (main project) geopandas repository.

The testing suite will run automatically on Travis-CI once your pull request is submitted. However, if you wish to run the test suite on a branch prior to submitting the pull request, then Travis-CI needs to be hooked up to your GitHub repository. Instructions for doing so are here.

### Creating a branch

You want your master branch to reflect only production-ready code, so create a feature branch for making your changes. For example:

    git branch shiny-new-feature
    git checkout shiny-new-feature

The above can be simplified to:

    git checkout -b shiny-new-feature

This changes your working directory to the shiny-new-feature branch. Keep any changes in this branch specific to one bug or feature so it is clear what the branch brings to geopandas. You can have many shiny-new-features and switch in between them using the git checkout command.

To update this branch, you need to retrieve the changes from the master branch:

    git fetch upstream
    git rebase upstream/master

This will replay your commits on top of the latest geopandas git master. If this leads to merge conflicts, you must resolve these before submitting your pull request. If you have uncommitted changes, you will need to `stash` them prior to updating. This will effectively store your changes and they can be reapplied after updating.

## 2) Creating a development environment

A development environment is a virtual space where you can keep an independent installation of geopandas. This makes it easy to keep both a stable version of python in one place you use for work, and a development version (which you may break while playing with code) in another.

An easy way to create a geopandas development environment is as follows:

- Install either Anaconda or miniconda
- Make sure that you have cloned the repository
- `cd` to the geopandas* source directory

Tell conda to create a new environment, named `geopandas_dev`, or any other name you would like for this environment, by running:

    conda create -n geopandas_dev

For a python 3 environment:

    conda create -n geopandas_dev python=3.4

This will create the new environment, and not touch any of your existing environments, nor any existing python installation.

To work in this environment, Windows users should `activate` it as follows:

    activate geopandas_dev

Mac OSX and Linux users should use:

    source activate geopandas_dev

You will then see a confirmation message to indicate you are in the new development environment.

To view your environments:

    conda info -e

To return to you home root environment:

    deactivate

See the full conda docs here.

At this point you can easily do a development install, as detailed in the next sections.

## 3) Installing Dependencies

To run geopandas in an development environment, you must first install geopandas’s dependencies. We suggest doing so using the following commands (executed after your development environment has been activated):

    conda install -c conda-forge fiona shapely pyproj rtree
    conda install pandas

This should install all necessary dependencies.

## 4) Making a development build

Once dependencies are in place, make an in-place build by navigating to the git clone of the geopandas repository and running:

    python setup.py develop

## 5) Making changes and writing tests

geopandas is serious about testing and strongly encourages contributors to embrace test-driven development (TDD). This development process “relies on the repetition of a very short development cycle: first the developer writes an (initially failing) automated test case that defines a desired improvement or new function, then produces the minimum amount of code to pass that test.” So, before actually writing any code, you should write your tests. Often the test can be taken from the original GitHub issue. However, it is always worth considering additional use cases and writing corresponding tests.

Adding tests is one of the most common requests after code is pushed to geopandas. Therefore, it is worth getting in the habit of writing tests ahead of time so this is never an issue.

geopandas uses the pytest testing system and the convenient extensions in numpy.testing.

### Writing tests

All tests should go into the `tests` directory. This folder contains many current examples of tests, and we suggest looking to these for inspiration.

The `.util` module has some special `assert` functions that make it easier to make statements about whether GeoSeries or GeoDataFrame objects are equivalent. The easiest way to verify that your code is correct is to explicitly construct the result you expect, then compare the actual result to the expected correct result, using eg the function `assert_geoseries_equal`.

### Running the test suite

The tests can then be run directly inside your Git clone (without having to install geopandas) by typing:

    pytest

## 6) Updating the Documentation

geopandas documentation resides in the doc folder. Changes to the docs are make by modifying the appropriate file in the source folder within doc. geopandas docs us reStructuredText syntax, which is explained here and the docstrings follow the Numpy Docstring standard.

Once you have made your changes, you can build the docs by navigating to the doc folder and typing:

    make html

The resulting html pages will be located in doc/build/html.

## 7) Submitting a Pull Request

Once you’ve made changes and pushed them to your forked repository, you then submit a pull request to have them integrated into the geopandas code base.

You can find a pull request (or PR) tutorial in the GitHub’s Help Docs.