Psycopg 3 -- PostgreSQL database adapter for Python

Psycopg 3 is a modern implementation of a PostgreSQL adapter for Python.

Installation

Quick version:

pip install --upgrade pip               # upgrade pip to at least 20.3
pip install "psycopg[binary,pool]"      # install binary dependencies

For further information about installation please check the documentation.

Hacking

In order to work on the Psycopg source code, you must have the libpq PostgreSQL client library installed on the system. For instance, on Debian systems, you can obtain it by running:

sudo apt install libpq5

On macOS, run:

brew install libpq

On Windows you can use EnterpriseDB's installers to obtain libpq which is included in the Command Line Tools.

You can then clone this repository to develop Psycopg:

git clone https://github.com/psycopg/psycopg.git
cd psycopg

Please note that the repository contains the source code of several Python packages, which may have different requirements:

The psycopg directory contains the pure python implementation of psycopg. The package has only a runtime dependency on the libpq, the PostgreSQL client library, which should be installed in your system.
The psycopg_c directory contains an optimization module written in C/Cython. In order to build it you will need a few development tools: please look at Local installation in the docs for the details.
The psycopg_pool directory contains the connection pools implementations. This is kept as a separate package to allow a different release cycle.

You can create a local virtualenv and install the packages in development mode, together with their development and testing requirements:

python -m venv .venv
source .venv/bin/activate
pip install -e "./psycopg[dev,test]"    # for the base Python package
pip install -e ./psycopg_pool           # for the connection pool
pip install ./psycopg_c                 # for the C speedup module

Please add --config-settings editable_mode=strict to the pip install -e above if you experience editable mode broken.

Now hack away! You can run the tests using:

psql -c 'create database psycopg_test'
export PSYCOPG_TEST_DSN="dbname=psycopg_test"
pytest

The library includes some pre-commit hooks to check that the code is valid according to the project coding convention. Please make sure to install them by running:

pre-commit install

This will allow to check lint errors before submitting merge requests, which will save you time and frustrations.

Cross-compiling

To use cross-platform zipapps created with shiv that include Psycopg as a dependency you must also have libpq installed. See the section above for install instructions.