annotate env/lib/python3.9/site-packages/boltons/typeutils.py @ 0:4f3585e2f14b draft default tip

"planemo upload commit 60cee0fc7c0cda8592644e1aad72851dec82c959"
author shellac
date Mon, 22 Mar 2021 18:12:50 +0000
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1 # -*- coding: utf-8 -*-
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2 """Python's built-in :mod:`functools` module builds several useful
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3 utilities on top of Python's first-class function support.
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4 ``typeutils`` attempts to do the same for metaprogramming with types
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5 and instances.
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6 """
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7
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8 from collections import deque
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9
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10 _issubclass = issubclass
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11
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12
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13 def make_sentinel(name='_MISSING', var_name=None):
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14 """Creates and returns a new **instance** of a new class, suitable for
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15 usage as a "sentinel", a kind of singleton often used to indicate
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16 a value is missing when ``None`` is a valid input.
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17
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18 Args:
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19 name (str): Name of the Sentinel
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20 var_name (str): Set this name to the name of the variable in
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21 its respective module enable pickleability.
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22
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23 >>> make_sentinel(var_name='_MISSING')
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24 _MISSING
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25
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26 The most common use cases here in boltons are as default values
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27 for optional function arguments, partly because of its
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28 less-confusing appearance in automatically generated
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29 documentation. Sentinels also function well as placeholders in queues
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30 and linked lists.
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31
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32 .. note::
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33
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34 By design, additional calls to ``make_sentinel`` with the same
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35 values will not produce equivalent objects.
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36
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37 >>> make_sentinel('TEST') == make_sentinel('TEST')
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38 False
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39 >>> type(make_sentinel('TEST')) == type(make_sentinel('TEST'))
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40 False
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41
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42 """
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43 class Sentinel(object):
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44 def __init__(self):
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45 self.name = name
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46 self.var_name = var_name
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47
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48 def __repr__(self):
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49 if self.var_name:
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50 return self.var_name
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51 return '%s(%r)' % (self.__class__.__name__, self.name)
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52 if var_name:
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53 def __reduce__(self):
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54 return self.var_name
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55
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56 def __nonzero__(self):
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57 return False
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58
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59 __bool__ = __nonzero__
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60
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61 return Sentinel()
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62
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63
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64 def issubclass(subclass, baseclass):
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65 """Just like the built-in :func:`issubclass`, this function checks
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66 whether *subclass* is inherited from *baseclass*. Unlike the
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67 built-in function, this ``issubclass`` will simply return
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68 ``False`` if either argument is not suitable (e.g., if *subclass*
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69 is not an instance of :class:`type`), instead of raising
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70 :exc:`TypeError`.
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71
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72 Args:
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73 subclass (type): The target class to check.
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74 baseclass (type): The base class *subclass* will be checked against.
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75
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76 >>> class MyObject(object): pass
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77 ...
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78 >>> issubclass(MyObject, object) # always a fun fact
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79 True
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80 >>> issubclass('hi', 'friend')
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81 False
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82 """
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83 try:
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84 return _issubclass(subclass, baseclass)
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85 except TypeError:
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86 return False
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87
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88
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89 def get_all_subclasses(cls):
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90 """Recursively finds and returns a :class:`list` of all types
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91 inherited from *cls*.
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92
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93 >>> class A(object):
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94 ... pass
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95 ...
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96 >>> class B(A):
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97 ... pass
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98 ...
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99 >>> class C(B):
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100 ... pass
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101 ...
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102 >>> class D(A):
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103 ... pass
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104 ...
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105 >>> [t.__name__ for t in get_all_subclasses(A)]
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106 ['B', 'D', 'C']
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107 >>> [t.__name__ for t in get_all_subclasses(B)]
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108 ['C']
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109
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110 """
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111 try:
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112 to_check = deque(cls.__subclasses__())
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113 except (AttributeError, TypeError):
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114 raise TypeError('expected type object, not %r' % cls)
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115 seen, ret = set(), []
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116 while to_check:
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117 cur = to_check.popleft()
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118 if cur in seen:
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119 continue
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120 ret.append(cur)
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121 seen.add(cur)
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122 to_check.extend(cur.__subclasses__())
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123 return ret
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124
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125
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126 class classproperty(object):
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127 """Much like a :class:`property`, but the wrapped get function is a
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128 class method. For simplicity, only read-only properties are
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129 implemented.
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130 """
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131
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132 def __init__(self, fn):
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133 self.fn = fn
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134
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135 def __get__(self, instance, cls):
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136 return self.fn(cls)