Adopt lazy imports from Terra

qiskit_optimization/algorithms/cplex_optimizer.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2020, 2021.
+# (C) Copyright IBM 2020, 2022.
 #
 # 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
@@ -15,25 +15,17 @@
 from typing import Any, Dict, Optional
 from warnings import warn
 
-from qiskit.exceptions import MissingOptionalLibraryError
-
 from qiskit_optimization.problems.quadratic_program import QuadraticProgram
 from qiskit_optimization.translators import to_docplex_mp
+import qiskit_optimization.optionals as _optionals
 from .optimization_algorithm import (
     OptimizationAlgorithm,
     OptimizationResult,
     OptimizationResultStatus,
 )
 
 
-try:
-    from cplex import Cplex  # pylint: disable=unused-import
-
-    _HAS_CPLEX = True
-except ImportError:
-    _HAS_CPLEX = False
-
-
+@_optionals.HAS_CPLEX.require_in_instance
 class CplexOptimizer(OptimizationAlgorithm):
     """The CPLEX optimizer wrapped as an Qiskit :class:`OptimizationAlgorithm`.
 
@@ -58,24 +50,14 @@ def __init__(
             disp: Whether to print CPLEX output or not.
             cplex_parameters: The parameters for CPLEX.
                 See https://www.ibm.com/docs/en/icos/20.1.0?topic=cplex-parameters for details.
-
-        Raises:
-            MissingOptionalLibraryError: CPLEX is not installed.
         """
-        if not _HAS_CPLEX:
-            raise MissingOptionalLibraryError(
-                libname="CPLEX",
-                name="CplexOptimizer",
-                pip_install="pip install 'qiskit-optimization[cplex]'",
-            )
-
         self._disp = disp
         self._cplex_parameters = cplex_parameters
 
     @staticmethod
     def is_cplex_installed():
         """Returns True if cplex is installed"""
-        return _HAS_CPLEX
+        return _optionals.HAS_CPLEX
 
     @property
     def disp(self) -> bool:

qiskit_optimization/algorithms/goemans_williamson_optimizer.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2021.
+# (C) Copyright IBM 2021, 2022.
 #
 # 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
@@ -18,8 +18,8 @@
 from typing import Optional, List, Tuple, Union, cast
 
 import numpy as np
-from qiskit.exceptions import MissingOptionalLibraryError
 
+import qiskit_optimization.optionals as _optionals
 from .optimization_algorithm import (
     OptimizationResult,
     OptimizationResultStatus,
@@ -30,15 +30,6 @@
 from ..problems.quadratic_program import QuadraticProgram
 from ..problems.variable import Variable
 
-try:
-    import cvxpy as cvx
-    from cvxpy import DCPError, DGPError, SolverError
-
-    _HAS_CVXPY = True
-except ImportError:
-    _HAS_CVXPY = False
-
-
 logger = logging.getLogger(__name__)
 
 
@@ -78,6 +69,7 @@ def sdp_solution(self) -> Optional[np.ndarray]:
         return self._sdp_solution
 
 
+@_optionals.HAS_CVXPY.require_in_instance
 class GoemansWilliamsonOptimizer(OptimizationAlgorithm):
     """
     Goemans-Williamson algorithm to approximate the max-cut of a problem.
@@ -103,16 +95,7 @@ def __init__(
             unique_cuts: The solve method returns only unique cuts, thus there may be less cuts
                 than ``num_cuts``.
             seed: A seed value for the random number generator.
-
-        Raises:
-            MissingOptionalLibraryError: CVXPY is not installed.
         """
-        if not _HAS_CVXPY:
-            raise MissingOptionalLibraryError(
-                libname="CVXPY",
-                name="GoemansWilliamsonOptimizer",
-                pip_install="pip install 'qiskit-optimization[cvxpy]'",
-            )
         super().__init__()
 
         self._num_cuts = num_cuts
@@ -148,6 +131,9 @@ def solve(self, problem: QuadraticProgram) -> OptimizationResult:
         Returns:
             cuts: A list of generated cuts.
         """
+        # pylint: disable=import-error
+        from cvxpy import DCPError, DGPError, SolverError
+
         self._verify_compatibility(problem)
 
         min2max = MinimizeToMaximize()
@@ -257,6 +243,9 @@ def _solve_max_cut_sdp(self, adj_matrix: np.ndarray) -> np.ndarray:
             chi: a list of length |V| where the i-th element is +1 or -1, representing which
                 set the it-h vertex is in. Returns None if an error occurs.
         """
+        # pylint: disable=import-error
+        import cvxpy as cvx
+
         num_vertices = len(adj_matrix)
         constraints, expr = [], 0
 

qiskit_optimization/algorithms/gurobi_optimizer.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2020, 2021.
+# (C) Copyright IBM 2020, 2022.
 #
 # 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
@@ -12,23 +12,14 @@
 
 """The Gurobi optimizer wrapped to be used within Qiskit's optimization module."""
 
-
-from qiskit.exceptions import MissingOptionalLibraryError
-
+import qiskit_optimization.optionals as _optionals
 from ..exceptions import QiskitOptimizationError
 from ..problems.quadratic_program import QuadraticProgram
 from ..translators.gurobipy import to_gurobipy
 from .optimization_algorithm import OptimizationAlgorithm, OptimizationResult
 
 
-try:
-    import gurobipy as gp
-
-    _HAS_GUROBI = True
-except ImportError:
-    _HAS_GUROBI = False
-
-
+@_optionals.HAS_GUROBIPY.require_in_instance
 class GurobiOptimizer(OptimizationAlgorithm):
     """The Gurobi optimizer wrapped as an Qiskit :class:`OptimizationAlgorithm`.
 
@@ -55,23 +46,13 @@ def __init__(self, disp: bool = False) -> None:
 
         Args:
             disp: Whether to print Gurobi output or not.
-
-        Raises:
-            MissingOptionalLibraryError: Gurobi is not installed.
         """
-        if not _HAS_GUROBI:
-            raise MissingOptionalLibraryError(
-                libname="GUROBI",
-                name="GurobiOptimizer",
-                pip_install="pip install qiskit-optimization[gurobi]",
-            )
-
         self._disp = disp
 
     @staticmethod
     def is_gurobi_installed():
         """Returns True if gurobi is installed"""
-        return _HAS_GUROBI
+        return _optionals.HAS_GUROBIPY
 
     @property
     def disp(self) -> bool:
@@ -120,6 +101,8 @@ def solve(self, problem: QuadraticProgram) -> OptimizationResult:
         Raises:
             QiskitOptimizationError: If the problem is incompatible with the optimizer.
         """
+        # pylint: disable=import-error
+        import gurobipy as gp
 
         # convert to Gurobi problem
         model = to_gurobipy(problem)

qiskit_optimization/applications/bin_packing.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2021.
+# (C) Copyright IBM 2021, 2022.
 #
 # 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
@@ -16,20 +16,16 @@
 
 import numpy as np
 from docplex.mp.model import Model
-from qiskit.exceptions import MissingOptionalLibraryError
 
+import qiskit_optimization.optionals as _optionals
 from qiskit_optimization.algorithms import OptimizationResult
 from qiskit_optimization.problems.quadratic_program import QuadraticProgram
 from qiskit_optimization.translators import from_docplex_mp
 from .optimization_application import OptimizationApplication
 
-try:
-    import matplotlib.pyplot as plt
+if _optionals.HAS_MATPLOTLIB:
     from matplotlib.pyplot import Figure
-
-    _HAS_MATPLOTLIB = True
-except ImportError:
-    _HAS_MATPLOTLIB = False
+else:
 
     class Figure:  # type: ignore
         """Empty Figure class
@@ -109,6 +105,7 @@ def interpret(self, result: Union[OptimizationResult, np.ndarray]) -> List[List[
         ]
         return items_in_bins
 
+    @_optionals.HAS_MATPLOTLIB.require_in_call
     def get_figure(self, result: Union[OptimizationResult, np.ndarray]) -> Figure:
         """Get plot of the solution of the Bin Packing Problem.
 
@@ -118,15 +115,9 @@ def get_figure(self, result: Union[OptimizationResult, np.ndarray]) -> Figure:
         Returns:
             fig: A plot of the solution, where x and y represent the bins and
             sum of the weights respectively.
-        Raises:
-            MissingOptionalLibraryError: if matplotlib is not installed.
         """
-        if not _HAS_MATPLOTLIB:
-            raise MissingOptionalLibraryError(
-                libname="matplotlib",
-                name="GraphOptimizationApplication",
-                pip_install="pip install 'qiskit-optimization[matplotlib]'",
-            )
+        import matplotlib.pyplot as plt
+
         colors = plt.cm.get_cmap("jet", len(self._weights))
         items_in_bins = self.interpret(result)
         num_bins = len(items_in_bins)

qiskit_optimization/applications/graph_optimization_application.py

@@ -1,6 +1,6 @@
 # This code is part of Qiskit.
 #
-# (C) Copyright IBM 2018, 2021.
+# (C) Copyright IBM 2018, 2022.
 #
 # 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
@@ -17,19 +17,12 @@
 
 import networkx as nx
 import numpy as np
-from qiskit.exceptions import MissingOptionalLibraryError
 
+import qiskit_optimization.optionals as _optionals
 from .optimization_application import OptimizationApplication
 from ..algorithms import OptimizationResult
 from ..deprecation import DeprecatedType, deprecate_method
 
-try:
-    import matplotlib as _
-
-    _HAS_MATPLOTLIB = True
-except ImportError:
-    _HAS_MATPLOTLIB = False
-
 
 class GraphOptimizationApplication(OptimizationApplication):
     """
@@ -46,6 +39,7 @@ def __init__(self, graph: Union[nx.Graph, np.ndarray, List]) -> None:
         # The view of the graph is stored which means the graph can not be changed.
         self._graph = nx.Graph(graph).copy(as_view=True)
 
+    @_optionals.HAS_MATPLOTLIB.require_in_call
     def draw(
         self,
         result: Optional[Union[OptimizationResult, np.ndarray]] = None,
@@ -57,16 +51,7 @@ def draw(
         Args:
             result: The calculated result for the problem
             pos: The positions of nodes
-        Raises:
-            MissingOptionalLibraryError: if matplotlib is not installed.
         """
-        if not _HAS_MATPLOTLIB:
-            raise MissingOptionalLibraryError(
-                libname="matplotlib",
-                name="GraphOptimizationApplication",
-                pip_install="pip install 'qiskit-optimization[matplotlib]'",
-            )
-
         if result is None:
             nx.draw(self._graph, pos=pos, with_labels=True)
         else:

qiskit_optimization/optionals.py

@@ -0,0 +1,49 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2022.
+#
+# 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.
+
+"""
+Additional optional constants.
+"""
+
+from qiskit.utils import LazyImportTester
+
+HAS_CPLEX = LazyImportTester(
+    {
+        "cplex": ("Cplex",),
+    },
+    name="CPLEX",
+    install="pip install 'qiskit-optimization[cplex]'",
+)
+
+HAS_CVXPY = LazyImportTester(
+    {
+        "cvxpy": ("DCPError", "DGPError", "SolverError"),
+    },
+    name="CVXPY",
+    install="pip install 'qiskit-optimization[cvx]'",
+)
+
+HAS_GUROBIPY = LazyImportTester(
+    {
+        "gurobipy": ("Model",),
+    },
+    name="Gurobi",
+    install="pip install 'qiskit-optimization[gurobi]'",
+)
+
+HAS_MATPLOTLIB = LazyImportTester(
+    {
+        "matplotlib.pyplot": ("Figure",),
+    },
+    name="Matplotlib",
+    install="pip install 'qiskit-optimization[matplotlib]'",
+)