Merge branch 'fixup/qsymm' into 'stable'

fix a bug in kwant.qsymm

See merge request kwant/kwant!325

INSTALL.rst

@@ -45,7 +45,7 @@ a NumPy-like Python package optimized for very small arrays,
 The following software is highly recommended though not strictly required:
  * `matplotlib <http://matplotlib.org/>`_ 1.5.1 or newer, for the module `kwant.plotter` and the tutorial,
  * `SymPy <http://sympy.org/>`_ 0.7.6 or newer, for the subpackage `kwant.continuum`.
- * `Qsymm <https://pypi.org/project/qsymm/>`_ 1.1.0 or newer, for the subpackage `kwant.qsymm`.
+ * `Qsymm <https://pypi.org/project/qsymm/>`_ 1.2.4 or newer, for the subpackage `kwant.qsymm`.
  * `MUMPS <http://graal.ens-lyon.fr/MUMPS/>`_, a sparse linear algebra library
    that will in many cases speed up Kwant several times and reduce the memory
    footprint.  (Kwant uses only the sequential, single core version

kwant/qsymm.py

@@ -323,8 +323,8 @@ def model_to_builder(model, norbs, lat_vecs, atom_coords, *, coeffs=None):
 
     # Keep track of the hoppings and onsites by storing those
     # which have already been set.
-    hopping_dict = defaultdict(dict)
-    onsites_dict = defaultdict(dict)
+    hopping_dict = defaultdict(lambda: 0)
+    onsites_dict = defaultdict(lambda: 0)
 
     # Iterate over all terms in the model.
     for key, hop_mat in model.items():

kwant/tests/test_qsymm.py

@@ -481,7 +481,7 @@ def test_find_cons_law():
                isinstance(symm, qsymm.ContinuousGroupGenerator) and symm.R is None]
     mham = builder_to_model(syst)
     assert all([symm.apply(mham).allclose(0, atol=1e-6) for symm in onsites])
-    
+
 
 def test_basis_ordering():
     symm_class = ['AI', 'D', 'AIII', 'BDI']

setup.py

@@ -588,7 +588,7 @@ def main():
               'plotting': 'matplotlib >= 1.5.1',
               'continuum': 'sympy >= 0.7.6',
               # qsymm is only packaged on PyPI
-              'qsymm': 'qsymm >= 1.1.2',
+              'qsymm': 'qsymm >= 1.2.4',
           },
           classifiers=[c.strip() for c in classifiers.split('\n')])