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| 1 | +"""Decimal fixed-point and floating-point arithmetic. |
| 2 | +
|
| 3 | +This is an implementation of decimal floating-point arithmetic based on |
| 4 | +the General Decimal Arithmetic Specification: |
| 5 | +
|
| 6 | + http://speleotrove.com/decimal/decarith.html |
| 7 | +
|
| 8 | +and IEEE standard 854-1987: |
| 9 | +
|
| 10 | + http://en.wikipedia.org/wiki/IEEE_854-1987 |
| 11 | +
|
| 12 | +Decimal floating point has finite precision with arbitrarily large bounds. |
| 13 | +
|
| 14 | +The purpose of this module is to support arithmetic using familiar |
| 15 | +"schoolhouse" rules and to avoid some of the tricky representation |
| 16 | +issues associated with binary floating point. The package is especially |
| 17 | +useful for financial applications or for contexts where users have |
| 18 | +expectations that are at odds with binary floating point (for instance, |
| 19 | +in binary floating point, 1.00 % 0.1 gives 0.09999999999999995 instead |
| 20 | +of 0.0; Decimal('1.00') % Decimal('0.1') returns the expected |
| 21 | +Decimal('0.00')). |
| 22 | +
|
| 23 | +Here are some examples of using the decimal module: |
| 24 | +
|
| 25 | +>>> from decimal import * |
| 26 | +>>> setcontext(ExtendedContext) |
| 27 | +>>> Decimal(0) |
| 28 | +Decimal('0') |
| 29 | +>>> Decimal('1') |
| 30 | +Decimal('1') |
| 31 | +>>> Decimal('-.0123') |
| 32 | +Decimal('-0.0123') |
| 33 | +>>> Decimal(123456) |
| 34 | +Decimal('123456') |
| 35 | +>>> Decimal('123.45e12345678') |
| 36 | +Decimal('1.2345E+12345680') |
| 37 | +>>> Decimal('1.33') + Decimal('1.27') |
| 38 | +Decimal('2.60') |
| 39 | +>>> Decimal('12.34') + Decimal('3.87') - Decimal('18.41') |
| 40 | +Decimal('-2.20') |
| 41 | +>>> dig = Decimal(1) |
| 42 | +>>> print(dig / Decimal(3)) |
| 43 | +0.333333333 |
| 44 | +>>> getcontext().prec = 18 |
| 45 | +>>> print(dig / Decimal(3)) |
| 46 | +0.333333333333333333 |
| 47 | +>>> print(dig.sqrt()) |
| 48 | +1 |
| 49 | +>>> print(Decimal(3).sqrt()) |
| 50 | +1.73205080756887729 |
| 51 | +>>> print(Decimal(3) ** 123) |
| 52 | +4.85192780976896427E+58 |
| 53 | +>>> inf = Decimal(1) / Decimal(0) |
| 54 | +>>> print(inf) |
| 55 | +Infinity |
| 56 | +>>> neginf = Decimal(-1) / Decimal(0) |
| 57 | +>>> print(neginf) |
| 58 | +-Infinity |
| 59 | +>>> print(neginf + inf) |
| 60 | +NaN |
| 61 | +>>> print(neginf * inf) |
| 62 | +-Infinity |
| 63 | +>>> print(dig / 0) |
| 64 | +Infinity |
| 65 | +>>> getcontext().traps[DivisionByZero] = 1 |
| 66 | +>>> print(dig / 0) |
| 67 | +Traceback (most recent call last): |
| 68 | + ... |
| 69 | + ... |
| 70 | + ... |
| 71 | +decimal.DivisionByZero: x / 0 |
| 72 | +>>> c = Context() |
| 73 | +>>> c.traps[InvalidOperation] = 0 |
| 74 | +>>> print(c.flags[InvalidOperation]) |
| 75 | +0 |
| 76 | +>>> c.divide(Decimal(0), Decimal(0)) |
| 77 | +Decimal('NaN') |
| 78 | +>>> c.traps[InvalidOperation] = 1 |
| 79 | +>>> print(c.flags[InvalidOperation]) |
| 80 | +1 |
| 81 | +>>> c.flags[InvalidOperation] = 0 |
| 82 | +>>> print(c.flags[InvalidOperation]) |
| 83 | +0 |
| 84 | +>>> print(c.divide(Decimal(0), Decimal(0))) |
| 85 | +Traceback (most recent call last): |
| 86 | + ... |
| 87 | + ... |
| 88 | + ... |
| 89 | +decimal.InvalidOperation: 0 / 0 |
| 90 | +>>> print(c.flags[InvalidOperation]) |
| 91 | +1 |
| 92 | +>>> c.flags[InvalidOperation] = 0 |
| 93 | +>>> c.traps[InvalidOperation] = 0 |
| 94 | +>>> print(c.divide(Decimal(0), Decimal(0))) |
| 95 | +NaN |
| 96 | +>>> print(c.flags[InvalidOperation]) |
| 97 | +1 |
| 98 | +>>> |
| 99 | +""" |
1 | 100 |
|
2 | 101 | try: |
3 | 102 | from _decimal import * |
4 | | - from _decimal import __doc__ |
5 | 103 | from _decimal import __version__ |
6 | 104 | from _decimal import __libmpdec_version__ |
7 | 105 | except ImportError: |
8 | | - from _pydecimal import * |
9 | | - from _pydecimal import __doc__ |
10 | | - from _pydecimal import __version__ |
11 | | - from _pydecimal import __libmpdec_version__ |
| 106 | + import _pydecimal |
| 107 | + import sys |
| 108 | + _pydecimal.__doc__ = __doc__ |
| 109 | + sys.modules[__name__] = _pydecimal |
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