Drop support for Python 3.7 (#10009)

* Drop support for Python 3.7

This updates our documentation and build processes to set Python 3.8 as
the oldest support version of Python, consistent with our policy on
Python support.

This commit also removes remaining Python-version gating, since we were
principally using this to account for differences between 3.7 and 3.8.
Several backport packages are no longer required for any suppported
Python version, because of this change.

* Remove test for multiprocessing on Mac

With Python 3.7 support now dropped, there are no versions of Python on
macOS that we expect to support with multiprocessing again.  There's no
guarantee that the hypothetical Python 10.11 (???) that this test was
previously checking would be any more valid than existing versions.

---------

Co-authored-by: Matthew Treinish <[email protected]>

.github/workflows/wheels.yml

@@ -17,7 +17,7 @@ jobs:
       - uses: actions/setup-python@v4
         name: Install Python
         with:
-          python-version: '3.7'
+          python-version: '3.10'
       - uses: dtolnay/rust-toolchain@stable
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v1
@@ -50,7 +50,7 @@ jobs:
       - uses: actions/setup-python@v4
         name: Install Python
         with:
-          python-version: '3.7'
+          python-version: '3.10'
       - uses: dtolnay/rust-toolchain@stable
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v1
@@ -83,7 +83,7 @@ jobs:
       - uses: actions/setup-python@v4
         name: Install Python
         with:
-          python-version: '3.7'
+          python-version: '3.10'
       - uses: dtolnay/rust-toolchain@stable
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v1

CONTRIBUTING.md

@@ -276,12 +276,12 @@ environment that tox sets up matches the CI environment more closely and it
 runs the tests in parallel (resulting in much faster execution). To run tests
 on all installed supported python versions and lint/style checks you can simply
 run `tox`. Or if you just want to run the tests once run for a specific python
-version: `tox -epy37` (or replace py37 with the python version you want to use,
-py35 or py36).
+version: `tox -epy310` (or replace py310 with the python version you want to use,
+py39 or py311).
 
 If you just want to run a subset of tests you can pass a selection regex to
 the test runner. For example, if you want to run all tests that have "dag" in
-the test id you can run: `tox -epy37 -- dag`. You can pass arguments directly to
+the test id you can run: `tox -epy310 -- dag`. You can pass arguments directly to
 the test runner after the bare `--`. To see all the options on test selection
 you can refer to the stestr manual:
 https://stestr.readthedocs.io/en/stable/MANUAL.html#test-selection
@@ -291,21 +291,21 @@ you can do this faster with the `-n`/`--no-discover` option. For example:
 
 to run a module:
 ```
-tox -epy37 -- -n test.python.test_examples
+tox -epy310 -- -n test.python.test_examples
 ```
 or to run the same module by path:
 
 ```
-tox -epy37 -- -n test/python/test_examples.py
+tox -epy310 -- -n test/python/test_examples.py
 ```
 to run a class:
 
 ```
-tox -epy37 -- -n test.python.test_examples.TestPythonExamples
+tox -epy310 -- -n test.python.test_examples.TestPythonExamples
 ```
 to run a method:
 ```
-tox -epy37 -- -n test.python.test_examples.TestPythonExamples.test_all_examples
+tox -epy310 -- -n test.python.test_examples.TestPythonExamples.test_all_examples
 ```
 
 Alternatively there is a makefile provided to run tests, however this

azure-pipelines.yml

@@ -34,12 +34,12 @@ parameters:
   - name: "supportedPythonVersions"
     displayName: "All supported versions of Python"
     type: object
-    default: ["3.7", "3.8", "3.9", "3.10", "3.11"]
+    default: ["3.8", "3.9", "3.10", "3.11"]
 
   - name: "minimumPythonVersion"
     displayName: "Minimum supported version of Python"
     type: string
-    default: "3.7"
+    default: "3.8"
 
   - name: "maximumPythonVersion"
     displayName: "Maximum supported version of Python"

pyproject.toml

@@ -4,12 +4,12 @@ build-backend = "setuptools.build_meta"
 
 [tool.black]
 line-length = 100
-target-version = ['py37', 'py38', 'py39', 'py310', 'py311']
+target-version = ['py38', 'py39', 'py310', 'py311']
 
 [tool.cibuildwheel]
 manylinux-x86_64-image = "manylinux2014"
 manylinux-i686-image = "manylinux2014"
-skip = "pp* cp36-* *musllinux*"
+skip = "pp* cp36-* cp37-* *musllinux*"
 test-skip = "cp310-win32 cp310-manylinux_i686 cp311-win32 cp311-manylinux_i686"
 test-command = "python {project}/examples/python/stochastic_swap.py"
 # We need to use pre-built versions of Numpy and Scipy in the tests; they have a

qiskit/__init__.py

@@ -21,15 +21,6 @@
 import qiskit._accelerate
 
 
-if sys.version_info < (3, 8):
-    warnings.warn(
-        "Using Qiskit with Python 3.7 is deprecated as of the 0.23.0 release. "
-        "Support for running Qiskit with Python 3.7 will be removed in the "
-        "0.25.0 release",
-        DeprecationWarning,
-    )
-
-
 # Globally define compiled submodules. The normal import mechanism will not find compiled submodules
 # in _accelerate because it relies on file paths, but PyO3 generates only one shared library file.
 # We manually define them on import so people can directly import qiskit._accelerate.* submodules

qiskit/algorithms/gradients/finite_diff_estimator_gradient.py

@@ -14,8 +14,8 @@
 
 from __future__ import annotations
 
-import sys
 from collections.abc import Sequence
+from typing import Literal
 
 import numpy as np
 
@@ -30,11 +30,6 @@
 
 from ..exceptions import AlgorithmError
 
-if sys.version_info >= (3, 8):
-    from typing import Literal
-else:
-    from typing_extensions import Literal
-
 
 class FiniteDiffEstimatorGradient(BaseEstimatorGradient):
     """

qiskit/algorithms/gradients/finite_diff_sampler_gradient.py

@@ -14,8 +14,8 @@
 
 from __future__ import annotations
 
-import sys
 from collections import defaultdict
+from typing import Literal, Sequence
 
 import numpy as np
 
@@ -28,12 +28,6 @@
 
 from ..exceptions import AlgorithmError
 
-if sys.version_info >= (3, 8):
-    # pylint: disable=ungrouped-imports
-    from typing import Literal, Sequence
-else:
-    from typing_extensions import Literal
-
 
 class FiniteDiffSamplerGradient(BaseSamplerGradient):
     """

qiskit/algorithms/optimizers/optimizer.py

@@ -18,20 +18,13 @@
 from collections.abc import Callable
 from enum import IntEnum
 import logging
-import sys
-from typing import Any, Union
+from typing import Any, Union, Protocol
 
 import numpy as np
 import scipy
 
 from qiskit.algorithms.algorithm_result import AlgorithmResult
 
-if sys.version_info >= (3, 8):
-    # pylint: disable=ungrouped-imports
-    from typing import Protocol
-else:
-    from typing_extensions import Protocol
-
 logger = logging.getLogger(__name__)
 
 POINT = Union[float, np.ndarray]

qiskit/algorithms/optimizers/p_bfgs.py

@@ -16,7 +16,6 @@
 import logging
 import multiprocessing
 import platform
-import sys
 from collections.abc import Callable
 from typing import SupportsFloat
 
@@ -109,12 +108,11 @@ def minimize(
             # default. The fork start method should be considered unsafe as it can
             # lead to crashes.
             # However P_BFGS doesn't support spawn, so we revert to single process.
-            if sys.version_info >= (3, 8):
-                num_procs = 0
-                logger.warning(
-                    "For MacOS, python >= 3.8, using only current process. "
-                    "Multiple core use not supported."
-                )
+            num_procs = 0
+            logger.warning(
+                "For MacOS, python >= 3.8, using only current process. "
+                "Multiple core use not supported."
+            )
         elif platform.system() == "Windows":
             num_procs = 0
             logger.warning(

qiskit/circuit/controlflow/switch_case.py

@@ -15,8 +15,7 @@
 __all__ = ("SwitchCaseOp", "CASE_DEFAULT")
 
 import contextlib
-import sys
-from typing import Union, Iterable, Any, Tuple, Optional, List
+from typing import Union, Iterable, Any, Tuple, Optional, List, Literal
 
 from qiskit.circuit import ClassicalRegister, Clbit, QuantumCircuit
 from qiskit.circuit.exceptions import CircuitError
@@ -25,11 +24,6 @@
 from .control_flow import ControlFlowOp
 from ._builder_utils import unify_circuit_resources, partition_registers
 
-if sys.version_info >= (3, 8):
-    from typing import Literal
-else:
-    from typing_extensions import Literal
-
 
 class _DefaultCaseType:
     """The type of the default-case singleton.  This is used instead of just having

qiskit/compiler/transpiler.py

@@ -19,9 +19,10 @@
 import logging
 import os
 import pickle
-import sys
 from time import time
 from typing import List, Union, Dict, Callable, Any, Optional, Tuple, Iterable, TypeVar
+from multiprocessing.shared_memory import SharedMemory
+from multiprocessing.managers import SharedMemoryManager
 import warnings
 
 from qiskit import user_config
@@ -48,12 +49,6 @@
 from qiskit.transpiler.timing_constraints import TimingConstraints
 from qiskit.transpiler.target import Target, target_to_backend_properties
 
-if sys.version_info >= (3, 8):
-    from multiprocessing.shared_memory import SharedMemory
-    from multiprocessing.managers import SharedMemoryManager
-else:
-    from shared_memory import SharedMemory, SharedMemoryManager
-
 logger = logging.getLogger(__name__)
 
 _CircuitT = TypeVar("_CircuitT", bound=Union[QuantumCircuit, List[QuantumCircuit]])

qiskit/pulse/builder.py

@@ -461,10 +461,10 @@
 import contextvars
 import functools
 import itertools
-import sys
 import uuid
 import warnings
 from contextlib import contextmanager
+from functools import singledispatchmethod
 from typing import (
     Any,
     Callable,
@@ -499,11 +499,6 @@
 from qiskit.pulse.schedule import Schedule, ScheduleBlock
 from qiskit.pulse.transforms.alignments import AlignmentKind
 
-if sys.version_info >= (3, 8):
-    from functools import singledispatchmethod
-else:
-    from singledispatchmethod import singledispatchmethod
-
 
 #: contextvars.ContextVar[BuilderContext]: active builder
 BUILDER_CONTEXTVAR = contextvars.ContextVar("backend")

qiskit/qasm2/__init__.py

@@ -385,9 +385,8 @@ def from_qasm_str(qasm_str: str):
 ]
 
 import os
-import sys
 from pathlib import Path
-from typing import Iterable, Union, Optional
+from typing import Iterable, Union, Optional, Literal
 
 # Pylint can't handle the C-extension introspection of `_qasm2` because there's a re-import through
 # to `qiskit.qasm2.exceptions`, and pylint ends up trying to import `_qasm2` twice, which PyO3
@@ -405,11 +404,6 @@ def from_qasm_str(qasm_str: str):
     LEGACY_CUSTOM_CLASSICAL,
 )
 
-if sys.version_info >= (3, 8):
-    from typing import Literal
-else:
-    from typing_extensions import Literal
-
 
 LEGACY_INCLUDE_PATH = (
     Path(__file__).parents[1] / "qasm" / "libs",

qiskit/qobj/converters/pulse_instruction.py

@@ -16,9 +16,9 @@
 
 import hashlib
 import re
-import sys
 import warnings
 from enum import Enum
+from functools import singledispatchmethod
 from typing import Union, List, Iterator, Optional
 import numpy as np
 
@@ -32,11 +32,6 @@
 from qiskit.qobj.utils import MeasLevel
 from qiskit.utils.deprecation import deprecate_func
 
-if sys.version_info >= (3, 8):
-    from functools import singledispatchmethod
-else:
-    from singledispatchmethod import singledispatchmethod
-
 
 class ParametricPulseShapes(Enum):
     """Map the assembled pulse names to the pulse module waveforms.

qiskit/tools/parallel.py

@@ -72,10 +72,7 @@ def get_platform_parallel_default():
         parallel_default = False
     # On macOS default false on Python >=3.8
     elif sys.platform == "darwin":
-        if sys.version_info[0] == 3 and sys.version_info[1] >= 8:
-            parallel_default = False
-        else:
-            parallel_default = True
+        parallel_default = False
     # On linux (and other OSes) default to True
     else:
         parallel_default = True

qiskit/transpiler/passes/basis/basis_translator.py

@@ -13,10 +13,10 @@
 
 """Translates gates to a target basis using a given equivalence library."""
 
-import sys
 import time
 import logging
 
+from functools import singledispatchmethod
 from itertools import zip_longest
 from collections import defaultdict
 
@@ -29,11 +29,6 @@
 from qiskit.transpiler.basepasses import TransformationPass
 from qiskit.transpiler.exceptions import TranspilerError
 
-if sys.version_info >= (3, 8):
-    from functools import singledispatchmethod
-else:
-    from singledispatchmethod import singledispatchmethod
-
 logger = logging.getLogger(__name__)
 
 

qiskit/utils/multiprocessing.py

@@ -14,7 +14,6 @@
 
 import multiprocessing as mp
 import platform
-import sys
 
 import psutil
 
@@ -44,14 +43,6 @@ def is_main_process():
     if platform.system() == "Windows":
         return not isinstance(mp.current_process(), mp.context.SpawnProcess)
     else:
-        return not (
-            isinstance(mp.current_process(), (mp.context.ForkProcess, mp.context.SpawnProcess))
-            # In python 3.5 and 3.6, processes created by "ProcessPoolExecutor" are not
-            # mp.context.ForkProcess or mp.context.SpawnProcess. As a workaround,
-            # "name" of the process is checked instead.
-            or (
-                sys.version_info[0] == 3
-                and (sys.version_info[1] == 5 or sys.version_info[1] == 6)
-                and mp.current_process().name != "MainProcess"
-            )
+        return not isinstance(
+            mp.current_process(), (mp.context.ForkProcess, mp.context.SpawnProcess)
         )