Decimal module: Processing of decimal

Source: Internet
Author: User
Decimal module: Processing of decimal

There is a large error in the float type with the decimal number in Python, which requires a decimal module to handle it.

definition of decimal:

>>> fromdecimalimport*

>>>x=decimal (' 0.70 ') *decimal (' 1.05 ')

>>> x

Decimal (' 0.7350 ')

Note: The str type is generally converted to the decimal type instead of float directly.

Rounding methods for decimal:

#quantize: Round method in the decimal module

>>> x.quantize (Decimal (' 0.01 ')) #round to nearest cent

Decimal (' 0.74 ')

>>>decimal (' 7.325 '). Quantize (Decimal (' 1. '), rounding=round_up)

Decimal (' 8 ')

Rounding mode: round_ceiling, Round_down, Round_floor, Round_half_down,round_half_even, Round_half_up, ROUND_UP, and ROUND_05UP .

Configuration changes:

# GetContext Method: View and set basic parameters. For example, set the exact digits of the desired decimal number.

>>> GetContext (). prec=36

>>> Decimal (1)/decimal (7)

Decimal (' 0.142857142857142857142857142857142857 ')

GetContext (). Rounding = Round_up

The transformation of the whole:

My_context=context (Prec=60,rounding=round_half_down)

SetContext (My_context) #转换为my_context

#模块自定义了常量BasicContext, Extendedcontext,defaultcontext.

#本质: Extendedcontext =getcontext (Basiccontext). Clear_flags ()

SetContext (Extendedcontext) #转换为ExtendedContext

other-string forwards for decimal:

data = Map (Decimal, ' 1.34 1.87 3.45 2.351.00 0.03 9.25 '. Split ())

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