The Lasagne project was started by Sander Dieleman in September 2014. It is developed by a core team of eight people (in alphabetical order: Eric Battenberg, Sander Dieleman, Daniel Nouri, Eben Olson, Aäron van den Oord, Colin Raffel, Jan Schlüter, Søren Kaae Sønderby) and numerous additional contributors on GitHub:

As an open-source project by researchers for researchers, we highly welcome contributions! Every bit helps and will be credited.


Lasagne grew out of a need to combine the flexibility of Theano with the availability of the right building blocks for training neural networks. Its development is guided by a number of design goals:

  • Simplicity: Be easy to use, easy to understand and easy to extend, to facilitate use in research. Interfaces should be kept small, with as few classes and methods as possible. Every added abstraction and feature should be carefully scrutinized, to determine whether the added complexity is justified.
  • Transparency: Do not hide Theano behind abstractions, directly process and return Theano expressions or Python / numpy data types. Try to rely on Theano’s functionality where possible, and follow Theano’s conventions.
  • Modularity: Allow all parts (layers, regularizers, optimizers, ...) to be used independently of Lasagne. Make it easy to use components in isolation or in conjunction with other frameworks.
  • Pragmatism: Make common use cases easy, do not overrate uncommon cases. Ideally, everything should be possible, but common use cases shouldn’t be made more difficult just to cater for exotic ones.
  • Restraint: Do not obstruct users with features they decide not to use. Both in using and in extending components, it should be possible for users to be fully oblivious to features they do not need.
  • Focus: “Do one thing and do it well”. Do not try to provide a library for everything to do with deep learning.

What to contribute

Give feedback

To send us general feedback, questions or ideas for improvement, please post on our mailing list.

If you have a very concrete feature proposal, add it to the issue tracker on GitHub:

  • Explain how it would work, and link to a scientific paper if applicable.
  • Keep the scope as narrow as possible, to make it easier to implement.

Report bugs

Report bugs at the issue tracker on GitHub. If you are reporting a bug, please include:

  • your Lasagne and Theano version.
  • steps to reproduce the bug, ideally reduced to a few Python commands.
  • the results you obtain, and the results you expected instead.

If you are unsure whether the behavior you experience is a bug, or if you are unsure whether it is related to Lasagne or Theano, please just ask on our mailing list first.

Fix bugs

Look through the GitHub issues for bug reports. Anything tagged with “bug” is open to whoever wants to implement it. If you discover a bug in Lasagne you can fix yourself, by all means feel free to just implement a fix and not report it first.

Implement features

Look through the GitHub issues for feature proposals. Anything tagged with “feature” or “enhancement” is open to whoever wants to implement it. If you have a feature in mind you want to implement yourself, please note that Lasagne has a fairly narrow focus and we strictly follow a set of design principles, so we cannot guarantee upfront that your code will be included. Please do not hesitate to just propose your idea in a GitHub issue or on the mailing list first, so we can discuss it and/or guide you through the implementation.

Write documentation

Whenever you find something not explained well, misleading, glossed over or just wrong, please update it! The Edit on GitHub link on the top right of every documentation page and the [source] link for every documented entity in the API reference will help you to quickly locate the origin of any text.

How to contribute

Edit on GitHub

As a very easy way of just fixing issues in the documentation, use the Edit on GitHub link on the top right of a documentation page or the [source] link of an entity in the API reference to open the corresponding source file in GitHub, then click the Edit this file link to edit the file in your browser and send us a Pull Request. All you need for this is a free GitHub account.

For any more substantial changes, please follow the steps below to setup Lasagne for development.

Development setup

First, follow the instructions for performing a development installation of Lasagne (including forking on GitHub): Development installation

To be able to run the tests and build the documentation locally, install additional requirements with: pip install -r requirements-dev.txt (adding --user if you want to install to your home directory instead).

If you use the bleeding-edge version of Theano, then instead of running that command, just use pip install to manually install all dependencies listed in requirements-dev.txt with their correct versions; otherwise it will attempt to downgrade Theano to the known good version in requirements.txt.


The documentation is generated with Sphinx. To build it locally, run the following commands:

cd docs
make html

Afterwards, open docs/_build/html/index.html to view the documentation as it would appear on readthedocs. If you changed a lot and seem to get misleading error messages or warnings, run make clean html to force Sphinx to recreate all files from scratch.

When writing docstrings, follow existing documentation as much as possible to ensure consistency throughout the library. For additional information on the syntax and conventions used, please refer to the following documents:


Lasagne has a code coverage of 100%, which has proven very helpful in the past, but also creates some duties:

  • Whenever you change any code, you should test whether it breaks existing features by just running the test suite. The test suite will also be run by Travis for any Pull Request to Lasagne.
  • Any code you add needs to be accompanied by tests ensuring that nobody else breaks it in future. Coveralls will check whether the code coverage stays at 100% for any Pull Request to Lasagne.
  • Every bug you fix indicates a missing test case, so a proposed bug fix should come with a new test that fails without your fix.

To run the full test suite, just do


Testing will take over 5 minutes for the first run, but less than a minute for subsequent runs when Theano can reuse compiled code. It will end with a code coverage report specifying which code lines are not covered by tests, if any. Furthermore, it will list any failed tests, and failed PEP8 checks.

To only run tests matching a certain name pattern, use the -k command line switch, e.g., -k pool will run the pooling layer tests only.

To land in a pdb debug prompt on a failure to inspect it more closely, use the --pdb switch.

Finally, for a loop-on-failing mode, do pip install pytest-xdist and run py.test -f. This will pause after the run, wait for any source file to change and run all previously failing tests again.

Sending Pull Requests

When you’re satisfied with your addition, the tests pass and the documentation looks good without any markup errors, commit your changes to a new branch, push that branch to your fork and send us a Pull Request via GitHub’s web interface.

All these steps are nicely explained on GitHub:

When filing your Pull Request, please include a description of what it does, to help us reviewing it. If it is fixing an open issue, say, issue #123, add Fixes #123, Resolves #123 or Closes #123 to the description text, so GitHub will close it when your request is merged.