Python interface for the igraph library
igraph is a library for creating and manipulating graphs. It is intended to be as powerful (ie. fast) as possible to enable the analysis of large graphs.
This repository contains the source code to the Python interface of igraph.
igraph is a collaborative work of many people from all around the world — see the list of contributors here.
Installation from PyPI
We aim to provide wheels on PyPI for most of the stock Python versions; typically at least the three most recent minor releases from Python 3.x. Therefore, running the following command should work without having to compile anything during installation:
pip install igraph
See details in Installing Python Modules.
Installation from source with pip on Debian / Ubuntu and derivatives
If you need to compile igraph from source for some reason, you need to install some dependencies first:
sudo apt install build-essential python-dev libxml2 libxml2-dev zlib1g-dev
and then run
pip install igraph
This should compile the C core of igraph as well as the Python extension automatically.
Installation from source on Windows
It is now also possible to compile
igraph from source under Windows for
Python 3.7 and later. Make sure that you have Microsoft Visual Studio 2015 or
later installed, and of course Python 3.7 or later. First extract the source to
a suitable directory. If you launch the Developer command prompt and navigate to
the directory where you extracted the source code, you should be able to build
and install igraph using
python setup.py install
You may need to set the architecture that you are building on explicitly by setting the environment variable
set IGRAPH_CMAKE_EXTRA_ARGS=-A [arch]
[arch] is either
Win32 for 32-bit builds or
x64 for 64-bit builds.
Also, when building in MSYS2, you need to set the
environment variable to
stdlib; this is because MSYS2 uses a patched version
distutils that conflicts with
setuptools >= 60.0.
By default, GraphML is disabled, because
libxml2 is not available on Windows in
the standard installation. You can install
libxml2 on Windows using
vcpkg. After installation of
libxml2 as follows
vcpkg.exe install libxml2:x64-windows-static-md
for 64-bit version (for 32-bit versions you can use the
triplet). You need to integrate
vcpkg in the build environment using
vcpkg.exe integrate install
This mentions that
CMake projects should use:
-DCMAKE_TOOLCHAIN_FILE=[vcpkg build script]
which we will do next. In order to build
igraph correctly, you also
need to set some other environment variables before building
set IGRAPH_CMAKE_EXTRA_ARGS=-DVCPKG_TARGET_TRIPLET=x64-windows-static-md -DCMAKE_TOOLCHAIN_FILE=[vcpkg build script] set IGRAPH_EXTRA_LIBRARY_PATH=[vcpkg directory]/installed/x64-windows-static-md/lib/ set IGRAPH_STATIC_EXTENSION=True set IGRAPH_EXTRA_LIBRARIES=libxml2,lzma,zlib,iconv,charset set IGRAPH_EXTRA_DYNAMIC_LIBRARIES: wsock32,ws2_32
You can now build and install
igraph again by simply running
python setup.py build. Please make sure to use a clean source tree, if you built
previously without GraphML, it will not update the build.
Linking to an existing igraph installation
The source code of the Python package includes the source code of the matching
igraph version that the Python interface should compile against. However, if
you want to link the Python interface to a custom installation of the C core
that has already been compiled and installed on your system, you can ask
setup.py to use the pre-compiled version. This option requires that your
custom installation of igraph is discoverable with
pkg-config. First, check
pkg-config can tell you the required compiler and linker flags for
pkg-config --cflags --libs igraph
pkg-config responds with a set of compiler and linker flags and not an
error message, you are probably okay. You can then proceed with the
installation using pip after setting the environment variable named
1 to indicate that you want to use an
igraph instance discoverable with
IGRAPH_USE_PKG_CONFIG=1 pip install igraph
Alternatively, if you have already downloaded and extracted the source code
of igraph, you can run
IGRAPH_USE_PKG_CONFIG=1 python setup.py build IGRAPH_USE_PKG_CONFIG=1 python setup.py install
(Note that you need the
IGRAPH_USE_PKG_CONFIG=1 environment variable
for both invocations, otherwise the call to
setup.py install would still
build the vendored C core instead of linking to an existing installation).
This option is primarily intended for package maintainers in Linux distributions so they can ensure that the packaged Python interface links to the packaged igraph library instead of bringing its own copy.
It is also useful on macOS if you want to link to the igraph library installed from Homebrew.
Due to the lack of support of
pkg-config on Windows, it is currently not
possible to build against an external library on Windows.
Warning: the Python interface is guaranteed to work only with the same
version of the C core that is vendored inside the
folder. While we try hard not to break API or ABI in the C core of igraph
between minor versions in the 0.x branch and we will keep on doing so for major
versions once 1.0 is released, there are certain functions in the C API that
are marked as experimental (see the documentation of the C core for details),
and we reserve the right to break the APIs of those functions, even if they are
already exposed in a higher-level interface. This is because the easiest way to
test these functions in real-life research scenarios is to expose them in one
of the higher level interfaces. Therefore, if you unbundle the vendored source
code of igraph and link to an external version instead, we can make no
guarantees about stability unless you link to the exact same version as the
one we have vendored in this source tree.
If you are curious about which version of the Python interface is compatible
with which version of the C core, you can look up the corresponding tag in
Github and check which revision of the C core the repository points to in
Compiling the development version
If you want to install the development version, the easiest way to do so is to install it using
pip install git+https://github.com/igraph/python-igraph
This automatically fetches the development version from the repository, builds
the package and installs it. By default, this will install the Python interface
main branch, which is used as the basis for the development of the
current release series. Unstable and breaking changes are being made in the
develop branch. You can install this similarly by doing
pip install git+https://github.com/igraph/python-igraph@develop
In addition to
git, the installation of the development version requires some
additional dependencies, read further below for details.
For more information about installing directly from
Alternatively, you can clone this repository locally. This repository contains a
matching version of the C core of
igraph as a git submodule. In order to
install the development version from source, you need to instruct git to check
out the submodules first:
git submodule update --init
Compiling the development version additionally requires
can install those on Ubuntu using
sudo apt install bison flex
On macOS you can install these from Homebrew or MacPorts. On Windows you can
winflexbison3 from Chocolatey.
Then, running the setup script should work if you have a C compiler and the necessary build dependencies (see also the previous section):
python setup.py build
You can install it using
python setup.py install
Running unit tests
Unit tests can be executed from within the repository directory with
with the built-in
python -m unittest
igraph are welcome!
If you want to add a feature, fix a bug, or suggest an improvement, open an issue on this repository and we'll try to answer. If you have a piece of code that you would like to see included in the main tree, open a PR on this repo.
To start developing
igraph, follow the steps above about installing the development version. Make sure that you do so by cloning the repository locally so that you are able to make changes.
For easier development, you can install
igraph in development mode so your changes in the Python source
code are picked up automatically by Python:
python setup.py develop
Changes that you make to the Python code do not need any extra action. However,
if you adjust the source code of the C extension, you need to rebuild it by running
python setup.py develop again. Compilation of the C core of
vendor/install so subsequent builds are much
faster than the first one as the C core does not need to be recompiled.
Supported Python versions
We aim to keep up with the development cycle of Python and support all official
Python versions that have not reached their end of life yet. Currently this
means that we support Python 3.7 to 3.11, inclusive. Please refer to this
page for the status of Python
branches and let us know if you encounter problems with
igraph on any
of the non-EOL Python versions.
Continuous integration tests are regularly executed on all non-EOL Python branches.
This version of igraph is compatible with PyPy and
is regularly tested on PyPy with
tox. However, the
PyPy version falls behind the CPython version in terms of performance; for
instance, running all the tests takes ~5 seconds on my machine with CPython and
~15 seconds with PyPy. This can probably be attributed to the need for
emulating CPython reference counting, and does not seem to be alleviated by the
There are also some subtle differences between the CPython and PyPy versions:
Docstrings defined in the C source code are not visible from PyPy.
GraphBaseis hashable and iterable in PyPy but not in CPython. Since
GraphBaseis internal anyway, this is likely to stay this way.