= Python Decimal =

'''`decimal`''' is a module providing utilities and APIs for working with fixed point and floating point numbers. 

<<TableOfContents>>

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== Usage ==

=== Decimal ===

A `decimal.Decimal` object can be instantiated with any of the following methods.

{{{
import decimal

decimal.Decimal('3.14')              #Decimal('3.14')
decimal.Decimal(3.14)                #Decimal('3.140000000000000124344978758017532527446746826171875')
decimal.Decimal((0, (3, 1, 4), -2))  #Decimal('3.14')
}}}

As demonstrated above, instantiating a `decimal.Decimal` object with a [[Python/Builtins/Types#Float|float]] is not likely to produce the desired result. When possible, construct numbers from strings. If an irrational number can be expressed as a fraction, compute it from `decimal.Decimal` objects.

{{{
d1 = decimal.Decimal(10)
d2 = decimal.Decimal(3)
d1 / d2                   #Decimal('3.3333333333333333333333333333')
}}}

There are also special values that can be instantiated like:

 * `decimal.Decimal('Infinity')`
 * `decimal.Decimal('-Infinity')`
 * `decimal.Decimal('NaN')`
 * `decimal.Decimal('-0')`

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=== Contexts ===

Implicitly, `decimal.Decimal` objects inherit a set of behavior configurations from the active thread's context.

To examine or overwrite the active thread's context, use `decimal.getcontext` and `decimal.setcontext`. The object returned by `decimal.getcontext` is also directly writeable.

{{{
import decimal

decimal.getcontext()  #Context(prec=28,
                          rounding=ROUND_HALF_EVEN,
                          Emin=-999999,
                          Emax=999999,
                          capitals=1,
                          clamp=0,
                          flags=[],
                          traps=[Overflow, DivisionByZero, InvalidOperation])

getcontext().prec += 2
}}}

It is also possible to use a local [[Python/ContextManager|context manager]].

{{{
import decimal

with decimal.localcontext() as ctx:
    ctx.prec = 42
    d = decimal.Decimal(10) / decimal.Decimal(3)

# The unary `+` operator rounds `d` to the active thread's precision
+d
}}}

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=== Constants ===

||'''Constant'''           ||'''Meaning'''                                                                                                      ||
||`decimal.ROUND_CEILING`  ||Round towards Infinity                                                                                             ||
||`decimal.ROUND_DOWN`     ||Round towards zero                                                                                                 ||
||`decimal.ROUND_FLOOR`    ||Round towards -Infinity                                                                                            ||
||`decimal.ROUND_HALF_DOWN`||Round to nearest with ties going towards zero                                                                      ||
||`decimal.ROUND_HALF_EVEN`||Round to nearest with ties going to nearest even integer                                                           ||
||`decimal.ROUND_HALF_UP`  ||Round to nearest with ties going away from zero                                                                    ||
||`decimal.ROUND_UP`       ||Round away from zero                                                                                               ||
||`decimal.ROUND_05UP`     ||Round away from zero if last digit after rounding towards zero would have been 0 or 5; otherwise round towards zero||

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== See also ==

[[https://docs.python.org/3/library/decimal.html|Python decimal module documentation]]

[[https://pymotw.com/3/decimal/|Python Module of the Day article for decimal]]



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