lint in the example files (Qiskit#4363)

Co-authored-by: Jay Gambetta <jay.gambetta@us.ibm.com>

Makefile

@@ -46,6 +46,7 @@ env:
 # Ignoring generated ones with .py extension.
 lint:
 	pylint -rn qiskit test
+        pylint -rn --disable='C0103, C0114, W0621' examples/python/*.py
 
 style:
 	pycodestyle --max-line-length=100 qiskit test

examples/python/commutation_relation.py

@@ -12,7 +12,7 @@
 # copyright notice, and modified files need to carry a notice indicating
 # that they have been altered from the originals.
 
-from qiskit import *
+from qiskit import QuantumCircuit
 
 from qiskit.transpiler import PassManager
 from qiskit.transpiler.passes import CommutationAnalysis, CommutativeCancellation
@@ -22,18 +22,18 @@
 circuit.cx(0, 1)
 circuit.cx(2, 1)
 circuit.cx(4, 3)
-circuit.cx(2, 3) 
+circuit.cx(2, 3)
 circuit.z(0)
 circuit.z(4)
 circuit.cx(0, 1)
 circuit.cx(2, 1)
 circuit.cx(4, 3)
-circuit.cx(2, 3) 
-circuit.cx(3, 2) 
+circuit.cx(2, 3)
+circuit.cx(3, 2)
 
 print(circuit)
 
 pm = PassManager()
 pm.append([CommutationAnalysis(), CommutativeCancellation()])
-new_circuit=pm.run(circuit)
+new_circuit = pm.run(circuit)
 print(new_circuit)

examples/python/load_qasm.py

@@ -15,7 +15,7 @@
 """Example on how to load a file into a QuantumCircuit."""
 
 from qiskit import QuantumCircuit
-from qiskit import QiskitError, execute, BasicAer
+from qiskit import execute, BasicAer
 
 circ = QuantumCircuit.from_qasm_file("examples/qasm/entangled_registers.qasm")
 print(circ)

examples/python/rippleadd.py

@@ -25,7 +25,7 @@
 # Set the backend name and coupling map.
 ###############################################################
 backend = BasicAer.get_backend("qasm_simulator")
-coupling_map = [[0,1], [0, 8], [1, 2], [1, 9], [2, 3], [2, 10], [3, 4], [3, 11],
+coupling_map = [[0, 1], [0, 8], [1, 2], [1, 9], [2, 3], [2, 10], [3, 4], [3, 11],
                 [4, 5], [4, 12], [5, 6], [5, 13], [6, 7], [6, 14], [7, 15], [8, 9],
                 [9, 10], [10, 11], [11, 12], [12, 13], [13, 14], [14, 15]]
 
@@ -38,7 +38,7 @@
 b = QuantumRegister(n, "b")
 cin = QuantumRegister(1, "cin")
 cout = QuantumRegister(1, "cout")
-ans = ClassicalRegister(n+1, "ans")
+ans = ClassicalRegister(n + 1, "ans")
 qc = QuantumCircuit(a, b, cin, cout, ans, name="rippleadd")
 
 
@@ -69,7 +69,7 @@ def unmajority(p, a, b, c):
 
 # Set the inputs to the adder
 qc.x(a[0])  # Set input a = 0...0001
-qc.x(b)   # Set input b = 1...1111
+qc.x(b)  # Set input b = 1...1111
 # Apply the adder
 qc += adder_subcircuit
 # Measure the output register in the computational basis

examples/python/stochastic_swap.py

@@ -15,8 +15,8 @@
 """Example of using the StochasticSwap pass."""
 
 from qiskit.transpiler.passes import StochasticSwap
-from qiskit.transpiler import CouplingMap, Layout
-from qiskit.converters import circuit_to_dag, dag_to_circuit
+from qiskit.transpiler import CouplingMap
+from qiskit.converters import circuit_to_dag
 from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
 
 coupling = CouplingMap([[0, 1], [1, 2], [1, 3]])

examples/python/using_qiskit_terra_level_0.py

@@ -18,27 +18,25 @@
 This example shows the most basic way to user Terra. It builds some circuits
 and runs them on both the BasicAer (local Qiskit provider) or IBMQ (remote IBMQ provider).
 
-To control the compile parameters we have provided a transpile function which can be used 
+To control the compile parameters we have provided a transpile function which can be used
 as a level 1 user.
 
 """
 
-import time
-
 # Import the Qiskit modules
-from qiskit import QuantumCircuit, QiskitError
+from qiskit import QuantumCircuit
 from qiskit import execute, BasicAer
 
 # making first circuit: bell state
 qc1 = QuantumCircuit(2, 2)
 qc1.h(0)
 qc1.cx(0, 1)
-qc1.measure([0,1], [0,1])
+qc1.measure([0, 1], [0, 1])
 
 # making another circuit: superpositions
 qc2 = QuantumCircuit(2, 2)
-qc2.h([0,1])
-qc2.measure([0,1], [0,1])
+qc2.h([0, 1])
+qc2.measure([0, 1], [0, 1])
 
 # setting up the backend
 print("(BasicAER Backends)")