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annotate planemo/lib/python3.7/site-packages/future/builtins/newround.py @ 1:56ad4e20f292 draft

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"planemo upload commit 6eee67778febed82ddd413c3ca40b3183a3898f1"
author guerler
date Fri, 31 Jul 2020 00:32:28 -0400
parents d30785e31577
children
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1 """
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2 ``python-future``: pure Python implementation of Python 3 round().
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3 """
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4
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5 from future.utils import PYPY, PY26, bind_method
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6
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7 # Use the decimal module for simplicity of implementation (and
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8 # hopefully correctness).
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9 from decimal import Decimal, ROUND_HALF_EVEN
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11
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12 def newround(number, ndigits=None):
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13 """
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14 See Python 3 documentation: uses Banker's Rounding.
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15
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16 Delegates to the __round__ method if for some reason this exists.
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17
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18 If not, rounds a number to a given precision in decimal digits (default
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19 0 digits). This returns an int when called with one argument,
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20 otherwise the same type as the number. ndigits may be negative.
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21
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22 See the test_round method in future/tests/test_builtins.py for
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23 examples.
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24 """
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25 return_int = False
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26 if ndigits is None:
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27 return_int = True
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28 ndigits = 0
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29 if hasattr(number, '__round__'):
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30 return number.__round__(ndigits)
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31
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32 if ndigits < 0:
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33 raise NotImplementedError('negative ndigits not supported yet')
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34 exponent = Decimal('10') ** (-ndigits)
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35
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36 if PYPY:
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37 # Work around issue #24: round() breaks on PyPy with NumPy's types
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38 if 'numpy' in repr(type(number)):
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39 number = float(number)
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40
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41 if isinstance(number, Decimal):
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42 d = number
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43 else:
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44 if not PY26:
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45 d = Decimal.from_float(number).quantize(exponent,
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46 rounding=ROUND_HALF_EVEN)
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47 else:
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48 d = from_float_26(number).quantize(exponent, rounding=ROUND_HALF_EVEN)
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49
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50 if return_int:
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51 return int(d)
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52 else:
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53 return float(d)
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54
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55
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56 ### From Python 2.7's decimal.py. Only needed to support Py2.6:
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57
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58 def from_float_26(f):
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59 """Converts a float to a decimal number, exactly.
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60
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61 Note that Decimal.from_float(0.1) is not the same as Decimal('0.1').
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62 Since 0.1 is not exactly representable in binary floating point, the
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63 value is stored as the nearest representable value which is
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64 0x1.999999999999ap-4. The exact equivalent of the value in decimal
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65 is 0.1000000000000000055511151231257827021181583404541015625.
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66
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67 >>> Decimal.from_float(0.1)
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68 Decimal('0.1000000000000000055511151231257827021181583404541015625')
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69 >>> Decimal.from_float(float('nan'))
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70 Decimal('NaN')
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71 >>> Decimal.from_float(float('inf'))
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72 Decimal('Infinity')
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73 >>> Decimal.from_float(-float('inf'))
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74 Decimal('-Infinity')
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75 >>> Decimal.from_float(-0.0)
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76 Decimal('-0')
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77
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78 """
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79 import math as _math
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80 from decimal import _dec_from_triple # only available on Py2.6 and Py2.7 (not 3.3)
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81
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82 if isinstance(f, (int, long)): # handle integer inputs
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83 return Decimal(f)
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84 if _math.isinf(f) or _math.isnan(f): # raises TypeError if not a float
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85 return Decimal(repr(f))
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86 if _math.copysign(1.0, f) == 1.0:
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87 sign = 0
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88 else:
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89 sign = 1
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90 n, d = abs(f).as_integer_ratio()
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91 # int.bit_length() method doesn't exist on Py2.6:
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92 def bit_length(d):
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93 if d != 0:
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94 return len(bin(abs(d))) - 2
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95 else:
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96 return 0
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97 k = bit_length(d) - 1
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98 result = _dec_from_triple(sign, str(n*5**k), -k)
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99 return result
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100
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101
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102 __all__ = ['newround']