mirror of https://github.com/python/cpython
gh-91291: Accept attributes as keyword arguments in decimal.localcontext (#32242)
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
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@ -925,12 +925,13 @@ Each thread has its own current context which is accessed or changed using the
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You can also use the :keyword:`with` statement and the :func:`localcontext`
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function to temporarily change the active context.
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.. function:: localcontext(ctx=None)
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.. function:: localcontext(ctx=None, \*\*kwargs)
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Return a context manager that will set the current context for the active thread
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to a copy of *ctx* on entry to the with-statement and restore the previous context
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when exiting the with-statement. If no context is specified, a copy of the
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current context is used.
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current context is used. The *kwargs* argument is used to set the attributes
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of the new context.
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For example, the following code sets the current decimal precision to 42 places,
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performs a calculation, and then automatically restores the previous context::
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@ -942,6 +943,21 @@ function to temporarily change the active context.
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s = calculate_something()
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s = +s # Round the final result back to the default precision
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Using keyword arguments, the code would be the following::
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from decimal import localcontext
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with localcontext(prec=42) as ctx:
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s = calculate_something()
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s = +s
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Raises :exc:`TypeError` if *kwargs* supplies an attribute that :class:`Context` doesn't
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support. Raises either :exc:`TypeError` or :exc:`ValueError` if *kwargs* supplies an
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invalid value for an attribute.
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.. versionchanged:: 3.11
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:meth:`localcontext` now supports setting context attributes through the use of keyword arguments.
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New contexts can also be created using the :class:`Context` constructor
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described below. In addition, the module provides three pre-made contexts:
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@ -441,6 +441,10 @@ import contextvars
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_current_context_var = contextvars.ContextVar('decimal_context')
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_context_attributes = frozenset(
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['prec', 'Emin', 'Emax', 'capitals', 'clamp', 'rounding', 'flags', 'traps']
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)
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def getcontext():
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"""Returns this thread's context.
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@ -464,7 +468,7 @@ def setcontext(context):
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del contextvars # Don't contaminate the namespace
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def localcontext(ctx=None):
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def localcontext(ctx=None, **kwargs):
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"""Return a context manager for a copy of the supplied context
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Uses a copy of the current context if no context is specified
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@ -500,8 +504,14 @@ def localcontext(ctx=None):
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>>> print(getcontext().prec)
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28
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"""
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if ctx is None: ctx = getcontext()
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return _ContextManager(ctx)
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if ctx is None:
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ctx = getcontext()
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ctx_manager = _ContextManager(ctx)
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for key, value in kwargs.items():
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if key not in _context_attributes:
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raise TypeError(f"'{key}' is an invalid keyword argument for this function")
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setattr(ctx_manager.new_context, key, value)
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return ctx_manager
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##### Decimal class #######################################################
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@ -3665,6 +3665,40 @@ class ContextWithStatement(unittest.TestCase):
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self.assertIsNot(new_ctx, set_ctx, 'did not copy the context')
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self.assertIs(set_ctx, enter_ctx, '__enter__ returned wrong context')
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def test_localcontext_kwargs(self):
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with self.decimal.localcontext(
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prec=10, rounding=ROUND_HALF_DOWN,
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Emin=-20, Emax=20, capitals=0,
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clamp=1
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) as ctx:
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self.assertEqual(ctx.prec, 10)
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self.assertEqual(ctx.rounding, self.decimal.ROUND_HALF_DOWN)
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self.assertEqual(ctx.Emin, -20)
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self.assertEqual(ctx.Emax, 20)
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self.assertEqual(ctx.capitals, 0)
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self.assertEqual(ctx.clamp, 1)
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self.assertRaises(TypeError, self.decimal.localcontext, precision=10)
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self.assertRaises(ValueError, self.decimal.localcontext, Emin=1)
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self.assertRaises(ValueError, self.decimal.localcontext, Emax=-1)
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self.assertRaises(ValueError, self.decimal.localcontext, capitals=2)
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self.assertRaises(ValueError, self.decimal.localcontext, clamp=2)
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self.assertRaises(TypeError, self.decimal.localcontext, rounding="")
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self.assertRaises(TypeError, self.decimal.localcontext, rounding=1)
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self.assertRaises(TypeError, self.decimal.localcontext, flags="")
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self.assertRaises(TypeError, self.decimal.localcontext, traps="")
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self.assertRaises(TypeError, self.decimal.localcontext, Emin="")
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self.assertRaises(TypeError, self.decimal.localcontext, Emax="")
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def test_local_context_kwargs_does_not_overwrite_existing_argument(self):
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ctx = self.decimal.getcontext()
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ctx.prec = 28
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with self.decimal.localcontext(prec=10) as ctx2:
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self.assertEqual(ctx.prec, 28)
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def test_nested_with_statements(self):
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# Use a copy of the supplied context in the block
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Decimal = self.decimal.Decimal
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@ -0,0 +1 @@
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:meth:`decimal.localcontext` now accepts context attributes via keyword arguments
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@ -1156,6 +1156,67 @@ context_setattr(PyObject *self, PyObject *name, PyObject *value)
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return PyObject_GenericSetAttr(self, name, value);
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}
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static int
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context_setattrs(PyObject *self, PyObject *prec, PyObject *rounding,
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PyObject *emin, PyObject *emax, PyObject *capitals,
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PyObject *clamp, PyObject *status, PyObject *traps) {
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int ret;
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if (prec != Py_None && context_setprec(self, prec, NULL) < 0) {
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return -1;
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}
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if (rounding != Py_None && context_setround(self, rounding, NULL) < 0) {
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return -1;
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}
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if (emin != Py_None && context_setemin(self, emin, NULL) < 0) {
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return -1;
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}
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if (emax != Py_None && context_setemax(self, emax, NULL) < 0) {
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return -1;
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}
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if (capitals != Py_None && context_setcapitals(self, capitals, NULL) < 0) {
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return -1;
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}
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if (clamp != Py_None && context_setclamp(self, clamp, NULL) < 0) {
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return -1;
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}
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if (traps != Py_None) {
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if (PyList_Check(traps)) {
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ret = context_settraps_list(self, traps);
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}
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#ifdef EXTRA_FUNCTIONALITY
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else if (PyLong_Check(traps)) {
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ret = context_settraps(self, traps, NULL);
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}
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#endif
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else {
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ret = context_settraps_dict(self, traps);
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}
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if (ret < 0) {
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return ret;
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}
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}
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if (status != Py_None) {
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if (PyList_Check(status)) {
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ret = context_setstatus_list(self, status);
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}
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#ifdef EXTRA_FUNCTIONALITY
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else if (PyLong_Check(status)) {
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ret = context_setstatus(self, status, NULL);
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}
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#endif
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else {
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ret = context_setstatus_dict(self, status);
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}
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if (ret < 0) {
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return ret;
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}
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}
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return 0;
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}
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static PyObject *
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context_clear_traps(PyObject *self, PyObject *dummy UNUSED)
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{
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@ -1255,7 +1316,6 @@ context_init(PyObject *self, PyObject *args, PyObject *kwds)
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PyObject *clamp = Py_None;
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PyObject *status = Py_None;
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PyObject *traps = Py_None;
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int ret;
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assert(PyTuple_Check(args));
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@ -1267,59 +1327,11 @@ context_init(PyObject *self, PyObject *args, PyObject *kwds)
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return -1;
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}
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if (prec != Py_None && context_setprec(self, prec, NULL) < 0) {
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return -1;
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}
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if (rounding != Py_None && context_setround(self, rounding, NULL) < 0) {
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return -1;
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}
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if (emin != Py_None && context_setemin(self, emin, NULL) < 0) {
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return -1;
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}
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if (emax != Py_None && context_setemax(self, emax, NULL) < 0) {
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return -1;
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}
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if (capitals != Py_None && context_setcapitals(self, capitals, NULL) < 0) {
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return -1;
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}
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if (clamp != Py_None && context_setclamp(self, clamp, NULL) < 0) {
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return -1;
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}
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if (traps != Py_None) {
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if (PyList_Check(traps)) {
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ret = context_settraps_list(self, traps);
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}
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#ifdef EXTRA_FUNCTIONALITY
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else if (PyLong_Check(traps)) {
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ret = context_settraps(self, traps, NULL);
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}
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#endif
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else {
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ret = context_settraps_dict(self, traps);
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}
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if (ret < 0) {
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return ret;
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}
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}
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if (status != Py_None) {
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if (PyList_Check(status)) {
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ret = context_setstatus_list(self, status);
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}
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#ifdef EXTRA_FUNCTIONALITY
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else if (PyLong_Check(status)) {
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ret = context_setstatus(self, status, NULL);
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}
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#endif
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else {
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ret = context_setstatus_dict(self, status);
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}
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if (ret < 0) {
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return ret;
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}
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}
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return 0;
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return context_setattrs(
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self, prec, rounding,
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emin, emax, capitals,
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clamp, status, traps
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);
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}
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static PyObject *
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@ -1721,13 +1733,28 @@ PyDec_SetCurrentContext(PyObject *self UNUSED, PyObject *v)
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static PyObject *
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ctxmanager_new(PyTypeObject *type UNUSED, PyObject *args, PyObject *kwds)
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{
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static char *kwlist[] = {"ctx", NULL};
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static char *kwlist[] = {
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"ctx", "prec", "rounding",
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"Emin", "Emax", "capitals",
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"clamp", "flags", "traps",
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NULL
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};
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PyDecContextManagerObject *self;
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PyObject *local = Py_None;
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PyObject *global;
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PyObject *prec = Py_None;
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PyObject *rounding = Py_None;
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PyObject *Emin = Py_None;
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PyObject *Emax = Py_None;
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PyObject *capitals = Py_None;
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PyObject *clamp = Py_None;
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PyObject *flags = Py_None;
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PyObject *traps = Py_None;
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CURRENT_CONTEXT(global);
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if (!PyArg_ParseTupleAndKeywords(args, kwds, "|O", kwlist, &local)) {
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if (!PyArg_ParseTupleAndKeywords(args, kwds, "|OOOOOOOOO", kwlist, &local,
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&prec, &rounding, &Emin, &Emax, &capitals, &clamp, &flags, &traps)) {
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return NULL;
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}
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if (local == Py_None) {
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self->global = global;
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Py_INCREF(self->global);
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int ret = context_setattrs(
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self->local, prec, rounding,
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Emin, Emax, capitals,
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clamp, flags, traps
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);
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if (ret < 0) {
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Py_DECREF(self);
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return NULL;
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}
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return (PyObject *)self;
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}
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@ -30,7 +30,7 @@ Set a new default context.\n\
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\n");
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PyDoc_STRVAR(doc_localcontext,
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"localcontext($module, /, ctx=None)\n--\n\n\
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"localcontext($module, /, ctx=None, **kwargs)\n--\n\n\
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Return a context manager that will set the default context to a copy of ctx\n\
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on entry to the with-statement and restore the previous default context when\n\
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exiting the with-statement. If no context is specified, a copy of the current\n\
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