Add a lazy loading wrapper class for __qiskit_version__

docs/apidocs/execute.rst

@@ -1,6 +1,6 @@
 .. _qiskit-execute:
 
-.. automodule:: qiskit.execute
+.. automodule:: qiskit.execute_function
    :no-members:
    :no-inherited-members:
    :no-special-members:

qiskit/__init__.py

@@ -73,14 +73,14 @@
 
 # Moved to after IBMQ and Aer imports due to import issues
 # with other modules that check for IBMQ (tools)
-from qiskit.execute import execute  # noqa
+from qiskit.execute_function import execute  # noqa
 from qiskit.compiler import transpile, assemble, schedule, sequence  # noqa
 
 from .version import __version__  # noqa
-from .version import _get_qiskit_versions  # noqa
+from .version import QiskitVersion  # noqa
 
 
-__qiskit_version__ = _get_qiskit_versions()
+__qiskit_version__ = QiskitVersion()
 
 
 if sys.version_info[0] == 3 and sys.version_info[1] == 6:

qiskit/compiler/__init__.py

@@ -30,7 +30,7 @@
 
 """
 
-from .assemble import assemble
-from .transpile import transpile
-from .schedule import schedule
-from .sequence import sequence
+from .assembler import assemble
+from .transpiler import transpile
+from .scheduler import schedule
+from .sequencer import sequence

qiskit/execute.py → qiskit/execute_function.py

@@ -11,11 +11,11 @@
 # that they have been altered from the originals.
 
 """
-=============================================
-Executing Experiments (:mod:`qiskit.execute`)
-=============================================
+======================================================
+Executing Experiments (:mod:`qiskit.execute_function`)
+======================================================
 
-.. currentmodule:: qiskit.execute
+.. currentmodule:: qiskit.execute_function
 
 .. autofunction:: execute
 """

qiskit/version.py

@@ -14,6 +14,7 @@
 
 """Contains the terra version."""
 
+from collections.abc import Mapping
 import os
 import subprocess
 import pkg_resources
@@ -81,35 +82,70 @@ def get_version_info():
 __version__ = get_version_info()
 
 
-def _get_qiskit_versions():
-    out_dict = {}
-    out_dict['qiskit-terra'] = __version__
-    try:
-        from qiskit.providers import aer
-        out_dict['qiskit-aer'] = aer.__version__
-    except Exception:
-        out_dict['qiskit-aer'] = None
-    try:
-        from qiskit import ignis
-        out_dict['qiskit-ignis'] = ignis.__version__
-    except Exception:
-        out_dict['qiskit-ignis'] = None
-    try:
-        from qiskit.providers import ibmq
-        out_dict['qiskit-ibmq-provider'] = ibmq.__version__
-    except Exception:
-        out_dict['qiskit-ibmq-provider'] = None
-    try:
-        from qiskit import aqua
-        out_dict['qiskit-aqua'] = aqua.__version__
-    except Exception:
-        out_dict['qiskit-aqua'] = None
-    try:
-        out_dict['qiskit'] = pkg_resources.get_distribution('qiskit').version
-    except Exception:
-        out_dict['qiskit'] = None
-
-    return out_dict
-
-
-__qiskit_version__ = _get_qiskit_versions()
+class QiskitVersion(Mapping):
+    """A lazy loading wrapper to get qiskit versions."""
+
+    __slots__ = ['_version_dict', '_loaded']
+
+    def __init__(self):
+        self._version_dict = {
+            'qiskit-terra': __version__,
+            'qiskit-aer': None,
+            'qiskit-ignis': None,
+            'qiskit-ibmq-provider': None,
+            'qiskit-aqua': None,
+            'qiskit': None}
+        self._loaded = False
+
+    def _load_versions(self):
+        try:
+            from qiskit.providers import aer
+            self._version_dict['qiskit-aer'] = aer.__version__
+        except Exception:
+            self._version_dict['qiskit-aer'] = None
+        try:
+            from qiskit import ignis
+            self._version_dict['qiskit-ignis'] = ignis.__version__
+        except Exception:
+            self._version_dict['qiskit-ignis'] = None
+        try:
+            from qiskit.providers import ibmq
+            self._version_dict['qiskit-ibmq-provider'] = ibmq.__version__
+        except Exception:
+            self._version_dict['qiskit-ibmq-provider'] = None
+        try:
+            from qiskit import aqua
+            self._version_dict['qiskit-aqua'] = aqua.__version__
+        except Exception:
+            self._version_dict['qiskit-aqua'] = None
+        try:
+            self._version_dict['qiskit'] = pkg_resources.get_distribution('qiskit').version
+        except Exception:
+            self._version_dict['qiskit'] = None
+        self._loaded = True
+
+    def __repr__(self):
+        if not self._loaded:
+            self._load_versions()
+        return repr(self._version_dict)
+
+    def __str__(self):
+        if not self._loaded:
+            self._load_versions()
+        return str(self._version_dict)
+
+    def __getitem__(self, key):
+        if not self._loaded:
+            self._load_versions()
+        return self._version_dict[key]
+
+    def __iter__(self):
+        if not self._loaded:
+            self._load_versions()
+        return iter(self._version_dict)
+
+    def __len__(self):
+        return len(self._version_dict)
+
+
+__qiskit_version__ = QiskitVersion()

releasenotes/notes/qiskit-version-wrapper-90cb7fcffeaafd6a.yaml

@@ -0,0 +1,45 @@
+---
+upgrade:
+  - |
+    The ``qiskit.__qiskit_version__`` module attribute was previously a ``dict``
+    will now return a custom read-only ``Mapping`` object that checks the
+    version of qiskit elements at runtime instead of at import time. This was
+    done to speed up the import path of qiskit and eliminate a possible import
+    cycle by only importing the element packages at runtime if the version
+    is needed from the package. This should be fully compatible with the
+    ``dict`` previously return and for most normal use cases there will be no
+    difference. However, if some applications were relying on either mutating
+    the contents or explicitly type checking it may require updates to adapt to
+    this change.
+  - |
+    The ``qiskit.execute`` module has been renamed to
+    :mod:`qiskit.execute_function`. This was necessary to avoid a potentical
+    name conflict between the :func:`~qiskit.execute_function.execute` function
+    which is re-exported as ``qiskit.execute``. ``qiskit.execute`` the function
+    in some situations could conflict with ``qiskit.execute`` the module which
+    would lead to a cryptic error because Python was treating ``qiskit.execute``
+    as the module when the intent was to the function or vice versa. The module
+    rename was necessary to avoid this conflict. If you're importing
+    ``qiskit.execute`` to get the module (typical usage was
+    ``from qiskit.execute import execute``) you will need to update this to
+    use ``qiskit.execute_function`` instead. ``qiskit.execute`` will now always
+    resolve to the function.
+  - |
+    The ``qiskit.compiler.transpile``, ``qiskit.compiler.assemble``,
+    ``qiskit.compiler.schedule``, and ``qiskit.compiler.sequence`` modules have
+    been renamed to ``qiskit.compiler.transpiler``,
+    ``qiskit.compiler.assembler``, ``qiskit.compiler.scheduler``, and
+    ``qiskit.compiler.sequence`` respectively. This was necessary to avoid a
+    potentical name conflict between the modules and the re-exported function
+    paths :func:`qiskit.compiler.transpile`, :func:`qiskit.compiler.assemble`,
+    :func:`qiskit.compiler.schedule`, and :func:`qiskit.compiler.sequence`.
+    In some situations this name conflict between the module path and
+    re-exported function path would lead to a cryptic error because Python was
+    treating an import as the module when the intent was to use the function or
+    vice versa. The module rename was necessary to avoid this conflict. If
+    you were using the imports to get the modules before (typical usage would
+    be like``from qiskit.compiler.transpile import transpile``) you will need
+    to update this to use the new module paths.
+    :func:`qiskit.compiler.transpile`, :func:`qiskit.compiler.assemble`,
+    :func:`qiskit.compiler.schedule`, and :func:`qiskit.compiler.sequence`
+    will now always resolve to the functions.

test/python/circuit/test_parameters.py

@@ -28,7 +28,7 @@
                             ParameterVector)
 from qiskit.circuit.exceptions import CircuitError
 from qiskit.compiler import assemble, transpile
-from qiskit.execute import execute
+from qiskit.execute_function import execute
 from qiskit import pulse
 from qiskit.quantum_info import Operator
 from qiskit.test import QiskitTestCase

test/python/compiler/test_assembler.py

@@ -21,7 +21,7 @@
 import qiskit.pulse as pulse
 from qiskit.circuit import Instruction, Gate, Parameter, ParameterVector, ParameterExpression
 from qiskit.circuit import QuantumRegister, ClassicalRegister, QuantumCircuit
-from qiskit.compiler.assemble import assemble
+from qiskit.compiler.assembler import assemble
 from qiskit.exceptions import QiskitError
 from qiskit.pulse import Schedule, Acquire, Play
 from qiskit.pulse.channels import MemorySlot, AcquireChannel, DriveChannel, MeasureChannel

test/python/compiler/test_disassembler.py

@@ -22,7 +22,7 @@
 from qiskit.assembler.run_config import RunConfig
 from qiskit.circuit import QuantumRegister, ClassicalRegister, QuantumCircuit
 from qiskit.circuit import Instruction
-from qiskit.compiler.assemble import assemble
+from qiskit.compiler.assembler import assemble
 from qiskit.test import QiskitTestCase
 from qiskit.test.mock import FakeOpenPulse2Q
 import qiskit.quantum_info as qi

test/python/providers/test_fake_backends.py

@@ -19,7 +19,7 @@
 from ddt import ddt, data
 
 from qiskit.circuit import QuantumCircuit
-from qiskit.execute import execute
+from qiskit.execute_function import execute
 from qiskit.test.base import QiskitTestCase
 from qiskit.test.mock import FakeProvider
 from qiskit.test.mock.fake_backend import HAS_AER

test/python/quantum_info/test_local_invariance.py

@@ -16,7 +16,7 @@
 import unittest
 
 from numpy.testing import assert_allclose
-from qiskit.execute import execute
+from qiskit.execute_function import execute
 from qiskit.circuit import QuantumCircuit, QuantumRegister
 from qiskit.test import QiskitTestCase
 from qiskit.providers.basicaer import UnitarySimulatorPy

test/python/test_version.py

@@ -0,0 +1,25 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2021
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+
+"""Tests for qiskit/version.py"""
+
+from qiskit import __qiskit_version__
+from qiskit import __version__
+from qiskit.test import QiskitTestCase
+
+
+class TestVersion(QiskitTestCase):
+    """Tests for qiskit/version.py"""
+
+    def test_qiskit_version(self):
+        """Test qiskit-version sets the correct version for terra."""
+        self.assertEqual(__version__, __qiskit_version__['qiskit-terra'])