Python:builtins

lastmod 2025-02-15created 2021-09-1314 edits

Types, functions, etc. built into (builtins) Python

exec

The isolated way to call exec with the fewest malfunctions is as follows:

from importlib import import_module


def get_annotations_compiler_flag() -> int:
    future = import_module("__future__")
    assert future is not None
    annotations = getattr(future, "annotations")
    assert annotations is not None
    compiler_flag = getattr(annotations, "compiler_flag")
    assert isinstance(compiler_flag, int)
    return compiler_flag


COMPILE_MODE_EXEC = "exec"
COMPILE_FLAGS = get_annotations_compiler_flag()


path = '/python/file/path.py'
global_variables = {}
with open(path, "r") as f:
    source = f.read()
ast = compile(source, path, COMPILE_MODE_EXEC, COMPILE_FLAGS)
exec(ast, global_variables, global_variables)

property

2. Built-in Functions — Python 3.6.12 documentation

Returns a property attribute.

class property(fget=None, fset=None, fdel=None, doc=None)

fget: a function for getting the attribute value.
fset: a function for setting the attribute value.
fdel: a function for deleting the attribute value.
doc: creates the docstring of the attribute.

class C:
    def __init__(self):
        self._x = None

    def getx(self):
        return self._x

    def setx(self, value):
        self._x = value

    def delx(self):
        del self._x

    x = property(getx, setx, delx, "I'm the 'x' property.")

Troubleshooting

NameError from the typing package in exec

Built-in Functions # compile

When running the exec() function, a Type Annotation-related error like the following may occur.

NameError: name 'List' is not defined

The first approach is to add code that enables Annotations Future to the code passed to exec().

from __future__ import annotations

Alternatively, add the above flag to the flags variable when calling compile(). The following shows how to obtain that flag. (See the related documentation for details):

from importlib import import_module


def get_annotations_compiler_flag() -> int:
    future = import_module("__future__")
    assert future is not None
    annotations = getattr(future, "annotations")
    assert annotations is not None
    compiler_flag = getattr(annotations, "compiler_flag")
    assert isinstance(compiler_flag, int)
    return compiler_flag

coverage.py malfunctions after exec

An AttributeError like the following may occur.

AttributeError: 'PosixPath' object has no attribute 'endswith'

The full Traceback is as follows:

Traceback (most recent call last):
  File "/home/yourid/Project/answer-dev/core/recc/http/http_app.py", line 178, in _runner
    await _run_app(
  File "/home/yourid/.pyenv/versions/opy-yourid-3.8.9/lib/python3.8/site-packages/aiohttp/web.py", line 319, in _run_app
    await runner.setup()
  File "/home/yourid/.pyenv/versions/opy-yourid-3.8.9/lib/python3.8/site-packages/aiohttp/web_runner.py", line 275, in setup
    self._server = await self._make_server()
  File "/home/yourid/.pyenv/versions/opy-yourid-3.8.9/lib/python3.8/site-packages/aiohttp/web_runner.py", line 375, in _make_server
    await self._app.startup()
  File "/home/yourid/.pyenv/versions/opy-yourid-3.8.9/lib/python3.8/site-packages/aiohttp/web_app.py", line 416, in startup
    await self.on_startup.send(self)
  File "/home/yourid/.pyenv/versions/opy-yourid-3.8.9/lib/python3.8/site-packages/aiohttp/signals.py", line 34, in send
    await receiver(*args, **kwargs)  # type: ignore
  File "/home/yourid/Project/answer-dev/core/recc/http/http_app.py", line 141, in on_startup
    await self._context.open()
  File "/home/yourid/Project/answer-dev/core/recc/core/context.py", line 85, in open
    self._plugins.create(self, *plugin_scripts)
  File "/home/yourid/Project/answer-dev/core/recc/plugin/plugin_manager.py", line 13, in create
    plugin = Plugin(file)
  File "/home/yourid/Project/answer-dev/core/recc/plugin/plugin.py", line 49, in __init__
    self._global_variables = exec_python_plugin(path)
  File "/home/yourid/Project/answer-dev/core/recc/plugin/plugin.py", line 40, in exec_python_plugin
    exec(ast, global_variables, local_variables)
  File "/home/yourid/.pyenv/versions/opy-yourid-3.8.9/lib/python3.8/site-packages/coverage/control.py", line 323, in _should_trace
    disp = self._inorout.should_trace(filename, frame)
  File "/home/yourid/.pyenv/versions/opy-yourid-3.8.9/lib/python3.8/site-packages/coverage/inorout.py", line 237, in should_trace
    filename = source_for_file(dunder_file)
  File "/home/yourid/.pyenv/versions/opy-yourid-3.8.9/lib/python3.8/site-packages/coverage/python.py", line 106, in source_for_file
    if filename.endswith(".py"):
AttributeError: 'PosixPath' object has no attribute 'endswith'

This happens because a pathlib.Path was passed as the filename (filename) during #compile. The filename (filename) argument of #compile must be passed as a str.

NameError when using Annotated assignment statements in exec

Use the same object for the exec() globals and locals arguments.

AttributeError when using dataclass in exec

When using dataclass, an error like the following may occur:

AttributeError: 'NoneType' object has no attribute '__dict__'

The full Traceback is as follows:

Traceback (most recent call last):

  ...

  File "/home/yourid/Project/answer-dev/core/recc/plugin/plugin.py", line 39, in __init__
    exec_python_plugin(path, global_variables, global_variables)
  File "/home/yourid/Project/answer-dev/core/recc/plugin/plugin.py", line 30, in exec_python_plugin
    exec(ast, global_variables, local_variables)
  File "/home/yourid/Project/answer-dev/core/storage/plugin/a4y.py", line 517, in <module>
    class A4yA:
  File "/home/yourid/.pyenv/versions/3.8.9/lib/python3.8/dataclasses.py", line 1019, in dataclass
    return wrap(cls)
  File "/home/yourid/.pyenv/versions/3.8.9/lib/python3.8/dataclasses.py", line 1011, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
  File "/home/yourid/.pyenv/versions/3.8.9/lib/python3.8/dataclasses.py", line 861, in _process_class
    cls_fields = [_get_field(cls, name, type)
  File "/home/yourid/.pyenv/versions/3.8.9/lib/python3.8/dataclasses.py", line 861, in <listcomp>
    cls_fields = [_get_field(cls, name, type)
  File "/home/yourid/.pyenv/versions/3.8.9/lib/python3.8/dataclasses.py", line 712, in _get_field
    and _is_type(f.type, cls, typing, typing.ClassVar,
  File "/home/yourid/.pyenv/versions/3.8.9/lib/python3.8/dataclasses.py", line 658, in _is_type
    ns = sys.modules.get(cls.__module__).__dict__
AttributeError: 'NoneType' object has no attribute '__dict__'

The Python code is as follows:

global_variables = {
    "__name__": "__recc_plugin__",
    "__file__": path,
}
with open(path, "r") as f:
    source = f.read()
ast = compile(source, path, COMPILE_MODE_EXEC, COMPILE_FLAGS)
exec(ast, global_variables, global_variables)

The problem is a chain reaction in the following order:

If __name__ is set in the global variables, the module with that name is used.
The cls argument passed to @dataclass is delivered as {module}.{class}.
So in the case above, cls is __recc_plugin__.A4yA.
cls.__module__ is '__recc_plugin__'.
sys.modules.get(cls.__module__) looks up the module named __recc_plugin__.
As a result, there is no such module, so it is None.

The fix is to remove all values passed in global_variables; then appropriate values are applied. (The module seems to be set to builtins)

The fixed code is as follows:

global_variables = {}
with open(path, "r") as f:
    source = f.read()
ast = compile(source, path, COMPILE_MODE_EXEC, COMPILE_FLAGS)
exec(ast, global_variables, global_variables)

For reference, see the Python:importlib page for how to load modules.

The annotations instance of a function symbol obtained from exec is `Dict[str, str]` instead of `Dict[str, type]`

In this case, reset annotations using the #eval function.

    def update_routes(self) -> None:
        routes = list()
        for method, path, guest_route in self._call_get_routes():
            host_route = deepcopy(guest_route)
            if hasattr(host_route, "__annotations__"):
                assert isinstance(host_route.__annotations__, dict)
                update_annotations: Dict[str, Any] = dict()
                for key, annotation in host_route.__annotations__.items():
                    if isinstance(annotation, type):
                        update_annotations[key] = annotation
                    else:
                        type_origin = eval(
                            annotation,
                            self._global_variables,
                            self._global_variables,
                        )
                        if type_origin is not None:
                            update_annotations[key] = type_origin
                        else:
                            update_annotations[key] = annotation
                host_route.__annotations__ = update_annotations
            routes.append(Route(method, path, host_route))
        self._routes = routes

Favorite site

[Recommended] Jump to Python - Built-in Functions ¹

References

Jump_to_Python_-_Builtin_Functions.pdf ↩

author Zer0 sitemap