All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.


[1.3.0] - 2020-11-01


  • integration test: run the tests for Kwant’s qsymm module against the current version of qsymm.


  • Avoided using deprecated functionality in latest scipy, numpy, and sympy

  • Fix syntax for python 3.9


  • Support of python < 3.7, numpy < 1.16, scipy < 1.1, sympy < 1.3 (similar to the upcoming Kwant release)

[1.2.6] - 2019-11-12


  • Downgraded scipy version requirement to 0.19, to maintain compatibility with Kwant

  • Correctly set model format when reshaping models with sparse values

[1.2.5] - 2019-11-11


  • Added basic reference documentation

  • Added citation instructions in

  • Added a tutorial with downloadable Python files and Jupyter notebooks


  • Allow ‘display_family’ to work when IPython is not installed

  • Bug when multiplying a model by a sympy expression (undefined variable)

  • Bug when multiplying BlochCoeff with sympy expression (sympy multiplication was being used, when BlochCoeff multiplication should have been used)

  • Remove copying of Sympy symbols (the hash values for the original and copy is different in some cases (probably a bug in Sympy)), which broke comparison between Models.

  • Remove ‘real’ assumption from Sympy symbols in ‘hamiltonian_from_family’; this makes all Sympy symbols in Qsymm consistently have no assumptions.

  • Minor clarifications to various docstrings


  • Removed the notebooks from the source repository

[1.2.4] - 2019-10-17


  • Set correct content-type on long description metadata

[1.2.3] - 2019-10-17


  • Add long description to package metadata

[1.2.2] - 2019-10-17


  • Adding zero to a model is now idempotent

[1.2.1] - 2019-09-02


  • Add


  • Restore compatibility with Python 3.5

[1.2.0] - 2019-08-30


  • Factory functions for discrete symmetries: time_reversal, particle_hole, chiral, inversion, rotation, mirror.

  • Better representation of PointGroupElements and ContinuousGroupGenerator, using _repr_pretty_ and _repr_latex_. Remove print_PG_elements and update example notebooks.

  • Implemented new functionality in Model:

    • Implement __matmul__ (@).

    • Support of sparse matrices and LinearOperator as values.

    • Consistent support of scalar valued Models.

    • Add keep to only keep track of certain symbolic coefficients.

    • More options and more transparent initialization, allow string keys which are automatically symmpified by default.

    • Several new utility functions, such as trace, reshape, allclose etc.


  • Slight change to the internal representation of PointGroupElements, allow mixing integer tinyarray with either sympy matrix or floating point tinyarray in the rotation part, but do not allow mixing the latter two representations. This removes the need to have two different representations for simple operators. Optimize multiplication by caching.

  • Changes in the API of Model:

    • Add format attribute to keep track of the type of data entries (i.e scalar, dense or sparse array).

    • Change the behaviour of * for Model objects, matrix multiplication only works with @ from now on. This breaks backward compatibility, a few uses in the qsymm code base were fixed.

    • Stop supporting a sequence of ints as momenta, instead string keys (e.g. 'k_x') or sympy expressions can be used. Certain other, rarely used ways to initialize Model don’t work anymore, some tests were changed accordingly.

    • Stop rounding and removing small entries from Model objects. This means that testing that the Model is empty is not a good test anymore to see if it is approximately zero. Use Model.allclose instead.

  • Optimizations in Model:

    • Remove unnecessary deep copying, which was slow.

    • Optimize the implementation of arithmetic operations to minimize number of loops and function calls.

    • Fast initialization by making restructuring optional when initialized with a dict.

    • Clean up the code of BlochModel to utilize improvements in Model.

    • Update symmetry finder to work with sparse models.


  • Deprecate initializing empty Model without providing shape and format.

[1.1.0] - 2018-12-05

Many of these changes were made in anticipation of integrating qsymm with kwant, allowing conversion between the Hamiltonian formats used.


  • BlochModel as a subclass of Model in order to store Bloch Hamiltonians with floating point hopping vectors.

  • bravais_point_group to find the point group of a Bravais lattice using the translation vectors only. This is intended for generating candidades for symmetries.


  • Change the way equality of Models is tested, the current implementation treats tolerances more consistently, this fixes some bugs in symmetry finding.

  • Allow using floating point rotation matrices in PointGroupElement.


  • Several bugs and internal code restructuring.