Function localcontext

Lib/_pydecimal.py:379–422

Return a context manager for a copy of the supplied context Uses a copy of the current context if no context is specified The returned context manager creates a local decimal context in a with statement: def sin(x): with localcontext() as ctx: ctx.p

(ctx=None, **kwargs)

del contextvars        # Don't contaminate the namespace

def localcontext(ctx=None, **kwargs):
    """Return a context manager for a copy of the supplied context

    Uses a copy of the current context if no context is specified
    The returned context manager creates a local decimal context
    in a with statement:
        def sin(x):
             with localcontext() as ctx:
                 ctx.prec += 2
                 # Rest of sin calculation algorithm
                 # uses a precision 2 greater than normal
             return +s  # Convert result to normal precision

         def sin(x):
             with localcontext(ExtendedContext):
                 # Rest of sin calculation algorithm
                 # uses the Extended Context from the
                 # General Decimal Arithmetic Specification
             return +s  # Convert result to normal context

    >>> setcontext(DefaultContext)
    >>> print(getcontext().prec)
    28
    >>> with localcontext():
    ...     ctx = getcontext()
    ...     ctx.prec += 2
    ...     print(ctx.prec)
    ...
    30
    >>> with localcontext(ExtendedContext):
    ...     print(getcontext().prec)
    ...
    9
    >>> print(getcontext().prec)
    28
    """
    if ctx is None:
        ctx = getcontext()
    ctx_manager = _ContextManager(ctx)
    for key, value in kwargs.items():
        if key not in _context_attributes:
            raise TypeError(f"'{key}' is an invalid keyword argument for this function")
        setattr(ctx_manager.new_context, key, value)
    return ctx_manager


def IEEEContext(bits, /):