Apply the Black code style to the source code (#95)

* Apply the Black code style

* Disable pep8 E203 check in code climate

* Add lint check to GitHub action

* Add black configuration for the max line length

.codeclimate.yml

@@ -37,6 +37,9 @@ plugins:
     enabled: true
   pep8:
     enabled: true
+    checks:
+      E203:
+        enabled: false
   duplication:
     enabled: true
     config:

.github/workflows/black.yml

@@ -0,0 +1,13 @@
+name: Lint
+
+on: [push, pull_request]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: psf/black@stable
+        with:
+          options: "--check --diff"
+          src: "./src"

pyproject.toml

@@ -5,3 +5,6 @@ requires = [
     "wheel",
 ]
 build-backend = "setuptools.build_meta"
+
+[tool.black]
+line-length = 79

src/qutip_qip/algorithms/qft.py

@@ -9,7 +9,7 @@
 from qutip import Qobj
 
 
-__all__ = ['qft', 'qft_steps', 'qft_gate_sequence']
+__all__ = ["qft", "qft_steps", "qft_gate_sequence"]
 
 
 def qft(N=1):
@@ -67,8 +67,9 @@ def qft_steps(N=1, swapping=True):
     else:
         for i in range(N):
             for j in range(i):
-                U_step_list.append(cphase(np.pi / (2 ** (i - j)), N,
-                                          control=i, target=j))
+                U_step_list.append(
+                    cphase(np.pi / (2 ** (i - j)), N, control=i, target=j)
+                )
             U_step_list.append(snot(N, i))
         if swapping:
             for i in range(N // 2):
@@ -104,9 +105,13 @@ def qft_gate_sequence(N=1, swapping=True):
     else:
         for i in range(N):
             for j in range(i):
-                qc.add_gate("CPHASE", targets=[j], controls=[i],
-                            arg_label=r"{\pi/2^{%d}}" % (i - j),
-                            arg_value=np.pi / (2 ** (i - j)))
+                qc.add_gate(
+                    "CPHASE",
+                    targets=[j],
+                    controls=[i],
+                    arg_label=r"{\pi/2^{%d}}" % (i - j),
+                    arg_value=np.pi / (2 ** (i - j)),
+                )
             qc.add_gate("SNOT", targets=[i])
         if swapping:
             for i in range(N // 2):