Add printable string representation for new Qobj objects

This commit adds a printable string representation for Qobj objects.
In Qiskit#3383 we rebuilt the Qobj objects without using marshmallow for
performance and ease of working with. However, as part of that no human
readable representation for the objects was added. This commit corrects
that oversight by adding a __str__ parameter to these new classes.

qiskit/qobj/pulse_qobj.py

@@ -19,6 +19,7 @@
 
 import copy
 import json
+import pprint
 
 import numpy
 
@@ -171,6 +172,16 @@ def to_dict(self):
                 x.to_dict() for x in self.discriminators]
         return out_dict
 
+    def __str__(self):
+        out = "Instruction: %s\n" % self.name
+        out += "\t\tt0: %s\n" % self.t0
+        for attr in ['ch', 'conditional', 'val', 'phase', 'duration',
+                     'qubits', 'memory_slot', 'register_slot',
+                     'label', 'type', 'pulse_shape', 'parameters']:
+            if hasattr(self, attr):
+                out += '\t\t%s: %s\n' % (attr, getattr(self, attr))
+        return out
+
     @classmethod
     def from_dict(cls, data):
         """Create a new PulseQobjExperimentConfig object from a dictionary.
@@ -319,6 +330,22 @@ def to_dict(self):
             out_dict['header'] = self.header.to_dict()
         return out_dict
 
+    def __str__(self):
+        out = '\nPulse Experiment:\n'
+        if hasattr(self, 'config'):
+            config = pprint.pformat(self.config.to_dict())
+        else:
+            config = '{}'
+        if hasattr(self, 'header'):
+            header = pprint.pformat(self.header.to_dict() or {})
+        else:
+            header = '{}'
+        out += 'Header:\n%s\n' % header
+        out += 'Config:\n%s\n\n' % config
+        for instruction in self.instructions:
+            out += '\t%s\n' % instruction
+        return out
+
     @classmethod
     def from_dict(cls, data):
         """Create a new PulseQobjExperiment object from a dictionary.
@@ -451,6 +478,17 @@ def default(self, obj):
         json_str = json.dumps(out_dict, cls=PulseQobjEncoder)
         validator(json.loads(json_str))
 
+    def __str__(self):
+        out = "Pulse Qobj: %s:\n" % self.qobj_id
+        config = pprint.pformat(self.config.to_dict())
+        out += "Config: %s\n" % str(config)
+        header = pprint.pformat(self.header.to_dict())
+        out += "Header: %s\n" % str(header)
+        out += "Experiments:\n"
+        for experiment in self.experiments:
+            out += "%s" % str(experiment)
+        return out
+
     def to_dict(self, validate=False):
         """Return a dictionary format representation of the Pulse Qobj.
 

qiskit/qobj/qasm_qobj.py

@@ -17,6 +17,7 @@
 """Module providing definitions of QASM Qobj classes."""
 
 import os
+import pprint
 from types import SimpleNamespace
 
 import json
@@ -122,6 +123,15 @@ def to_dict(self):
 
         return out_dict
 
+    def __str__(self):
+        out = "Instruction: %s\n" % self.name
+        for attr in ['params', 'qubits', 'register', 'memory', '_condition',
+                     'conditional', 'label', 'mask', 'relation', 'val',
+                     'snapshot_type']:
+            if hasattr(self, attr):
+                out += '\t\t%s: %s\n' % (attr, getattr(self, attr))
+        return out
+
     @classmethod
     def from_dict(cls, data):
         """Create a new QasmQobjInstruction object from a dictionary.
@@ -161,6 +171,16 @@ def __init__(self, config=None, header=None, instructions=None):
         self.header = header or QasmQobjExperimentHeader()
         self.instructions = instructions or []
 
+    def __str__(self):
+        out = '\nQASM Experiment:\n'
+        config = pprint.pformat(self.config.to_dict())
+        header = pprint.pformat(self.header.to_dict())
+        out += 'Header:\n%s\n' % header
+        out += 'Config:\n%s\n\n' % config
+        for instruction in self.instructions:
+            out += '\t%s\n' % instruction
+        return out
+
     def to_dict(self):
         """Return a dictionary format representation of the Experiment.
 
@@ -364,6 +384,17 @@ def __init__(self, qobj_id=None, config=None, experiments=None,
         self.experiments = experiments or []
         self.qobj_id = qobj_id
 
+    def __str__(self):
+        out = "QASM Qobj: %s:\n" % self.qobj_id
+        config = pprint.pformat(self.config.to_dict())
+        out += "Config: %s\n" % str(config)
+        header = pprint.pformat(self.header.to_dict())
+        out += "Header: %s\n" % str(header)
+        out += "Experiments:\n"
+        for experiment in self.experiments:
+            out += "%s" % str(experiment)
+        return out
+
     def to_dict(self, validate=False):
         """Return a dictionary format representation of the QASM Qobj.