Add flake8 and isort checks on python files in cpp folder (#2838)

* Add flake8 checks on python files in cpp folder

* flake8 fixes in cpp

* Add isort checks on python files in cpp folder

* Move flake8 marker to root directory

* Remove python/.flake8

.github/workflows/ccpp.yml

@@ -67,13 +67,21 @@ jobs:
 
       - name: Flake8 checks
         run: |
+          cd cpp/
+          python3 -m flake8 cmake
+          python3 -m flake8 demo
+          python3 -m flake8 test
+          cd ..
           cd python/
           python3 -m flake8 dolfinx
           python3 -m flake8 demo
           python3 -m flake8 test
       - name: isort checks (non-blocking)
         continue-on-error: true
         run: |
+          cd cpp/
+          python3 -m isort --check .
+          cd ..
           cd python/
           python3 -m isort --check .
       - name: mypy checks

cpp/demo/hyperelasticity/hyperelasticity.py

@@ -37,9 +37,9 @@
 
 # Kinematics
 d = len(u)
-I = Identity(d)         # Identity tensor
+I = Identity(d)         # Identity tensor  # noqa: E741
 F = variable(I + grad(u))         # Deformation gradient
-C = F.T*F               # Right Cauchy-Green tensor
+C = F.T * F               # Right Cauchy-Green tensor
 
 # Invariants of deformation tensors
 Ic = tr(C)
@@ -52,18 +52,18 @@
 # Elasticity parameters
 E = 10.0
 nu = 0.3
-mu = E/(2*(1 + nu))
-lmbda = E*nu/((1 + nu)*(1 - 2*nu))
+mu = E / (2 * (1 + nu))
+lmbda = E * nu / ((1 + nu) * (1 - 2 * nu))
 
 # Both the first variation of the potential energy, and the Jacobian of
 # the variation, can be automatically computed by a call to
 # ``derivative``::
 
 # Stored strain energy density (compressible neo-Hookean model)
-psi = (mu/2)*(Ic - 3) - mu*ln(J) + (lmbda/2)*(ln(J))**2
+psi = (mu / 2) * (Ic - 3) - mu * ln(J) + (lmbda / 2) * (ln(J))**2
 
 # Total potential energy
-Pi = psi*dx  # - inner(B, u)*dx - inner(T, u)*ds
+Pi = psi * dx  # - inner(B, u) * dx - inner(T, u) * ds
 
 # First variation of Pi (directional derivative about u in the direction of v)
 F_form = derivative(Pi, u, v)
@@ -72,7 +72,7 @@
 J_form = derivative(F_form, u, du)
 
 # Compute Cauchy stress
-sigma = (1/J)*diff(psi, F)*F.T
+sigma = (1 / J) * diff(psi, F) * F.T
 
 forms = [F_form, J_form]
 elements = [e]

cpp/demo/poisson_matrix_free/poisson.py

@@ -4,7 +4,7 @@
 from ufl import (Coefficient, Constant, FunctionSpace, Mesh, TestFunction,
                  TrialFunction, action, dx, grad, inner)
 
-coord_element = element("Lagrange", "triangle", 1,  shape=(2,))
+coord_element = element("Lagrange", "triangle", 1, shape=(2,))
 mesh = Mesh(coord_element)
 
 # Function Space

cpp/test/poisson.py

@@ -1,9 +1,9 @@
-from ufl import (Coefficient, Constant, FunctionSpace, Mesh,
-                 TestFunction, TrialFunction, dx, grad, inner)
 from basix.ufl import element
+from ufl import (Coefficient, Constant, FunctionSpace, Mesh, TestFunction,
+                 TrialFunction, dx, grad, inner)
 
 e = element("Lagrange", "tetrahedron", 2)
-coord_element = element("Lagrange", "tetrahedron", 1,  shape=(3,))
+coord_element = element("Lagrange", "tetrahedron", 1, shape=(3,))
 mesh = Mesh(coord_element)
 
 V = FunctionSpace(mesh, e)