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Package gnue :: Package common :: Package external :: Module decimal

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Module gnue.common.external.decimal

This is a Py2.3 implementation of decimal floating point arithmetic based on
the General Decimal Arithmetic Specification:

    www2.hursley.ibm.com/decimal/decarith.html

and IEEE standard 854-1987:

    www.cs.berkeley.edu/~ejr/projects/754/private/drafts/854-1987/dir.html

Decimal floating point has finite precision with arbitrarily large bounds.

The purpose of the module is to support arithmetic using familiar
"schoolhouse" rules and to avoid the some of tricky representation
issues associated with binary floating point.  The package is especially
useful for financial applications or for contexts where users have
expectations that are at odds with binary floating point (for instance,
in binary floating point, 1.00 % 0.1 gives 0.09999999999999995 instead
of the expected Decimal("0.00") returned by decimal floating point).

Here are some examples of using the decimal module:

>>> from decimal import *
>>> setcontext(ExtendedContext)
>>> Decimal(0)
Decimal("0")
>>> Decimal("1")
Decimal("1")
>>> Decimal("-.0123")
Decimal("-0.0123")
>>> Decimal(123456)
Decimal("123456")
>>> Decimal("123.45e12345678901234567890")
Decimal("1.2345E+12345678901234567892")
>>> Decimal("1.33") + Decimal("1.27")
Decimal("2.60")
>>> Decimal("12.34") + Decimal("3.87") - Decimal("18.41")
Decimal("-2.20")
>>> dig = Decimal(1)
>>> print dig / Decimal(3)
0.333333333
>>> getcontext().prec = 18
>>> print dig / Decimal(3)
0.333333333333333333
>>> print dig.sqrt()
1
>>> print Decimal(3).sqrt()
1.73205080756887729
>>> print Decimal(3) ** 123
4.85192780976896427E+58
>>> inf = Decimal(1) / Decimal(0)
>>> print inf
Infinity
>>> neginf = Decimal(-1) / Decimal(0)
>>> print neginf
-Infinity
>>> print neginf + inf
NaN
>>> print neginf * inf
-Infinity
>>> print dig / 0
Infinity
>>> getcontext().traps[DivisionByZero] = 1
>>> print dig / 0
Traceback (most recent call last):
  ...
  ...
  ...
DivisionByZero: x / 0
>>> c = Context()
>>> c.traps[InvalidOperation] = 0
>>> print c.flags[InvalidOperation]
0
>>> c.divide(Decimal(0), Decimal(0))
Decimal("NaN")
>>> c.traps[InvalidOperation] = 1
>>> print c.flags[InvalidOperation]
1
>>> c.flags[InvalidOperation] = 0
>>> print c.flags[InvalidOperation]
0
>>> print c.divide(Decimal(0), Decimal(0))
Traceback (most recent call last):
  ...
  ...
  ...
InvalidOperation: 0 / 0
>>> print c.flags[InvalidOperation]
1
>>> c.flags[InvalidOperation] = 0
>>> c.traps[InvalidOperation] = 0
>>> print c.divide(Decimal(0), Decimal(0))
NaN
>>> print c.flags[InvalidOperation]
1
>>>

---

Classes
Context	Contains the context for a Decimal instance.
Decimal	Floating point class for decimal arithmetic.

Exceptions
Clamped	Exponent of a 0 changed to fit bounds.
DecimalException	Base exception class.
DivisionByZero	Division by 0.
Inexact	Had to round, losing information.
InvalidOperation	An invalid operation was performed.
Overflow	Numerical overflow.
Rounded	Number got rounded (not necessarily changed during rounding).
Subnormal	Exponent < Emin before rounding.
Underflow	Numerical underflow with result rounded to 0.

Function Summary
	getcontext(_local) Returns this thread's context.
	setcontext(context, _local) Set this thread's context to context.

Variable Summary
Context	BasicContext = Context(prec=9, rounding=ROUND_HALF_UP, E...
Context	DefaultContext = Context(prec=28, rounding=ROUND_HALF_EV...
Context	ExtendedContext = Context(prec=9, rounding=ROUND_HALF_EV...
str	ROUND_CEILING = 'ROUND_CEILING'
str	ROUND_DOWN = 'ROUND_DOWN'
str	ROUND_FLOOR = 'ROUND_FLOOR'
str	ROUND_HALF_DOWN = 'ROUND_HALF_DOWN'
str	ROUND_HALF_EVEN = 'ROUND_HALF_EVEN'
str	ROUND_HALF_UP = 'ROUND_HALF_UP'
str	ROUND_UP = 'ROUND_UP'

Function Details

getcontext(_local=<thread._local object at 0xb77501e8>) Returns this thread's context. If this thread does not yet have a context, returns a new context and sets this thread's context. New contexts are copies of DefaultContext.

setcontext(context, _local=<thread._local object at 0xb77501e8>) Set this thread's context to context.

Variable Details

BasicContext Type: Context Value: Context(prec=9, rounding=ROUND_HALF_UP, Emin=-999999999, Emax=99999999\ 9, capitals=1, flags=[], traps=[Overflow, InvalidOperation, Underflow,\ DivisionByZero, Clamped])

DefaultContext Type: Context Value: Context(prec=28, rounding=ROUND_HALF_EVEN, Emin=-999999999, Emax=99999\ 9999, capitals=1, flags=[], traps=[Overflow, InvalidOperation, Divisio\ nByZero])

ExtendedContext Type: Context Value: Context(prec=9, rounding=ROUND_HALF_EVEN, Emin=-999999999, Emax=999999\ 999, capitals=1, flags=[], traps=[])

ROUND_CEILING Type: str Value: 'ROUND_CEILING'

ROUND_DOWN Type: str Value: 'ROUND_DOWN'

ROUND_FLOOR Type: str Value: 'ROUND_FLOOR'

ROUND_HALF_DOWN Type: str Value: 'ROUND_HALF_DOWN'

ROUND_HALF_EVEN Type: str Value: 'ROUND_HALF_EVEN'

ROUND_HALF_UP Type: str Value: 'ROUND_HALF_UP'

ROUND_UP Type: str Value: 'ROUND_UP'

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