Tidy up examples (#2191)

* Fixed teleport example

* Tidied up 3 other examples

* Tidied up some print statements

examples/python/commutation_relation.py

@@ -1,7 +1,7 @@
 from qiskit import *
 
 from qiskit.transpiler import PassManager
-from qiskit.transpiler.passes import CommutationAnalysis, CommutationTransformation
+from qiskit.transpiler.passes import CommutationAnalysis, CommutativeCancellation
 from qiskit.transpiler import transpile
 
 qr = QuantumRegister(5, 'qr')
@@ -23,7 +23,7 @@ print(circuit.draw())
 
 pm = PassManager()
 
-pm.append([CommutationAnalysis(), CommutationTransformation()])
+pm.append([CommutationAnalysis(), CommutativeCancellation()])
 
 # TODO make it not needed to have a backend 
 backend_device = BasicAer.get_backend('qasm_simulator')

examples/python/ghz.py

@@ -20,18 +20,19 @@ from qiskit.providers.ibmq import least_busy
 ###############################################################
 # Make a quantum circuit for the GHZ state.
 ###############################################################
-q = QuantumRegister(5, "q")
-c = ClassicalRegister(5, "c")
+num_qubits = 5
+q = QuantumRegister(num_qubits, "q")
+c = ClassicalRegister(num_qubits, "c")
 qc = QuantumCircuit(q, c, name='ghz')
 
 # Create a GHZ state
 qc.h(q[0])
-for i in range(4):
+for i in range(num_qubits-1):
     qc.cx(q[i], q[i+1])
 # Insert a barrier before measurement
 qc.barrier()
 # Measure all of the qubits in the standard basis
-for i in range(5):
+for i in range(num_qubits):
     qc.measure(q[i], c[i])
 
 ###############################################################
@@ -48,7 +49,7 @@ except:
 sim_backend = BasicAer.get_backend('qasm_simulator')
 job = execute(qc, sim_backend, shots=1024)
 result = job.result()
-print('Qasm simulator')
+print('Qasm simulator : ')
 print(result.get_counts(qc))
 
 # Second version: real device
@@ -57,4 +58,5 @@ least_busy_device = least_busy(IBMQ.backends(simulator=False,
 print("Running on current least busy device: ", least_busy_device)
 job = execute(qc, least_busy_device, shots=1024)
 result = job.result()
+print('Physical device (%s) : ' % least_busy_device)
 print(result.get_counts(qc))

examples/python/hello_quantum.py

@@ -60,7 +60,7 @@ try:
     result_exp = job_exp.result()
 
     # Show the results
-    print(result_exp.get_counts(qc))
+    print('Counts: ', result_exp.get_counts(qc))
 
 except QiskitError as ex:
     print('There was an error in the circuit!. Error = {}'.format(ex))

examples/python/initialize.py

@@ -56,7 +56,7 @@ print(circuit.qasm())
 shots = 10000
 
 # Desired vector
-print("Desired probabilities...")
+print("Desired probabilities: ")
 print(str(list(map(lambda x: format(abs(x * x), '.3f'), desired_vector))))
 
 # Initialize on local simulator
@@ -64,11 +64,11 @@ sim_backend = BasicAer.get_backend('qasm_simulator')
 job = execute(circuit, sim_backend, shots=shots)
 result = job.result()
 
-print("Probabilities from simulator...[%s]" % result)
 n_qubits_qureg = qr.size
 counts = result.get_counts(circuit)
 
 qubit_strings = [format(i, '0%sb' % n_qubits_qureg) for
                  i in range(2 ** n_qubits_qureg)]
+print("Probabilities from simulator: ")
 print([format(counts.get(s, 0) / shots, '.3f') for
        s in qubit_strings])

examples/python/qft.py

@@ -14,8 +14,8 @@ used `pip install`, the examples only work from the root directory.
 
 import math
 from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
-from qiskit import execute, BasicAer, IBMQ
-from qiskit.providers.ibmq import least_busy
+from qiskit import execute, BasicAer
+from qiskit.providers.ibmq import least_busy, IBMQ
 
 
 ###############################################################

examples/python/teleport.py

@@ -59,7 +59,9 @@ qc.measure(q[2], c2[0])
 ###############################################################
 
 # First version: not mapped
-initial_layout = [q[0], q[1], q[2]]
+initial_layout = {q[0]: 0,
+                  q[1]: 1,
+                  q[2]: 2}
 job = execute(qc, backend=backend, coupling_map=None, shots=1024, initial_layout=initial_layout)
 
 result = job.result()