Compatibility problems with sympy 1.8
Hi, I'm new to QSymm and I'm just running through the tutorials from readthedocs. It appears to me that whenever I try to convert a string hamiltonian with J>=1, it returns some error codes. 
This is part of the tutorial code that I downloaded from the readthedocs. I've also tried to use J=1, but it returns a similar error:
The details of the error codes are attached below:
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
ValueError: Error from parse_expr with transformed code: "Symbol ('hbar' )**Integer (2 )/(Integer (2 )*Symbol ('m' ))*(k_x **Integer (2 )+k_y **Integer (2 )+k_z **Integer (2 ))*eye (Integer (4 ))+Symbol ('alpha' )*J_x *k_x +Symbol ('alpha' )*J_y *k_y +Symbol ('alpha' )*J_z *k_z "
The above exception was the direct cause of the following exception:
TypeError Traceback (most recent call last)
<ipython-input-14-b84411f42ce9> in <module>
4 "alpha * J_x * k_x + alpha * J_y * k_y + alpha * J_z * k_z"
5 )
----> 6 H_rashba = qsymm.Model(ham_rashba, locals=dict(J_x=J_x, J_y=J_y, J_z=J_z))
7 H_rashba.tosympy(nsimplify=True)
~/opt/anaconda3/lib/python3.8/site-packages/qsymm/model.py in __init__(self, hamiltonian, locals, momenta, keep, symbol_normalizer, normalize, shape, format)
205 else:
206 # Try to parse the input with kwant_continuum.sympify
--> 207 hamiltonian = kwant_continuum.sympify(hamiltonian, locals=locals)
208 if not isinstance(hamiltonian, MatrixBase):
209 hamiltonian = sympy.Matrix([[hamiltonian]])
~/opt/anaconda3/lib/python3.8/site-packages/qsymm/kwant_continuum.py in sympify(expr, locals)
213 stored_value = converter.pop(list, None)
214 converter[list] = lambda x: sympy.Matrix(x)
--> 215 hamiltonian = sympy.sympify(expr, locals=locals)
216 # if input is for example ``[[k_x * A(x) * k_x]]`` after the first
217 # sympify we are getting list of sympy objects, so we call sympify
~/opt/anaconda3/lib/python3.8/site-packages/sympy/core/sympify.py in sympify(a, locals, convert_xor, strict, rational, evaluate)
477 try:
478 a = a.replace('\n', '')
--> 479 expr = parse_expr(a, local_dict=locals, transformations=transformations, evaluate=evaluate)
480 except (TokenError, SyntaxError) as exc:
481 raise SympifyError('could not parse %r' % a, exc)
~/opt/anaconda3/lib/python3.8/site-packages/sympy/parsing/sympy_parser.py in parse_expr(s, local_dict, transformations, global_dict, evaluate)
1016 return eval_expr(code, local_dict, global_dict)
1017 except Exception as e:
-> 1018 raise e from ValueError(f"Error from parse_expr with transformed code: {code!r}")
1019
1020
~/opt/anaconda3/lib/python3.8/site-packages/sympy/parsing/sympy_parser.py in parse_expr(s, local_dict, transformations, global_dict, evaluate)
1014
1015 try:
-> 1016 return eval_expr(code, local_dict, global_dict)
1017 except Exception as e:
1018 raise e from ValueError(f"Error from parse_expr with transformed code: {code!r}")
~/opt/anaconda3/lib/python3.8/site-packages/sympy/parsing/sympy_parser.py in eval_expr(code, local_dict, global_dict)
908 Generally, ``parse_expr`` should be used.
909 """
--> 910 expr = eval(
911 code, global_dict, local_dict) # take local objects in preference
912 return expr
<string> in <module>
TypeError: unsupported operand type(s) for +: 'MutableDenseMatrix' and 'ImmutableDenseNDimArray'
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
ValueError: Error from parse_expr with transformed code: "Symbol ('hbar' )**Integer (2 )/(Integer (2 )*Symbol ('m' ))*(k_x **Integer (2 )+k_y **Integer (2 )+k_z **Integer (2 ))*eye (Integer (4 ))+Symbol ('alpha' )*J_x *k_x +Symbol ('alpha' )*J_y *k_y +Symbol ('alpha' )*J_z *k_z "
The above exception was the direct cause of the following exception:
TypeError Traceback (most recent call last)
<ipython-input-14-b84411f42ce9> in <module>
4 "alpha * J_x * k_x + alpha * J_y * k_y + alpha * J_z * k_z"
5 )
----> 6 H_rashba = qsymm.Model(ham_rashba, locals=dict(J_x=J_x, J_y=J_y, J_z=J_z))
7 H_rashba.tosympy(nsimplify=True)
~/opt/anaconda3/lib/python3.8/site-packages/qsymm/model.py in __init__(self, hamiltonian, locals, momenta, keep, symbol_normalizer, normalize, shape, format)
205 else:
206 # Try to parse the input with kwant_continuum.sympify
--> 207 hamiltonian = kwant_continuum.sympify(hamiltonian, locals=locals)
208 if not isinstance(hamiltonian, MatrixBase):
209 hamiltonian = sympy.Matrix([[hamiltonian]])
~/opt/anaconda3/lib/python3.8/site-packages/qsymm/kwant_continuum.py in sympify(expr, locals)
213 stored_value = converter.pop(list, None)
214 converter[list] = lambda x: sympy.Matrix(x)
--> 215 hamiltonian = sympy.sympify(expr, locals=locals)
216 # if input is for example ``[[k_x * A(x) * k_x]]`` after the first
217 # sympify we are getting list of sympy objects, so we call sympify
~/opt/anaconda3/lib/python3.8/site-packages/sympy/core/sympify.py in sympify(a, locals, convert_xor, strict, rational, evaluate)
477 try:
478 a = a.replace('\n', '')
--> 479 expr = parse_expr(a, local_dict=locals, transformations=transformations, evaluate=evaluate)
480 except (TokenError, SyntaxError) as exc:
481 raise SympifyError('could not parse %r' % a, exc)
~/opt/anaconda3/lib/python3.8/site-packages/sympy/parsing/sympy_parser.py in parse_expr(s, local_dict, transformations, global_dict, evaluate)
1016 return eval_expr(code, local_dict, global_dict)
1017 except Exception as e:
-> 1018 raise e from ValueError(f"Error from parse_expr with transformed code: {code!r}")
1019
1020
~/opt/anaconda3/lib/python3.8/site-packages/sympy/parsing/sympy_parser.py in parse_expr(s, local_dict, transformations, global_dict, evaluate)
1014
1015 try:
-> 1016 return eval_expr(code, local_dict, global_dict)
1017 except Exception as e:
1018 raise e from ValueError(f"Error from parse_expr with transformed code: {code!r}")
~/opt/anaconda3/lib/python3.8/site-packages/sympy/parsing/sympy_parser.py in eval_expr(code, local_dict, global_dict)
908 Generally, ``parse_expr`` should be used.
909 """
--> 910 expr = eval(
911 code, global_dict, local_dict) # take local objects in preference
912 return expr
<string> in <module>
TypeError: unsupported operand type(s) for +: 'MutableDenseMatrix' and 'ImmutableDenseNDimArray'Edited by Anton Akhmerov