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1 #! /usr/bin/env python
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2 # Copyright (c) 2010 Chortos-2 <chortos@inbox.lv>
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3
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4 # A compatibility layer for Python 2.5+. This is what lets test.py
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5 # run on all versions of Python starting with 2.5, including Python 3.
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6
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7 # A few notes regarding some compatibility-driven peculiarities
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8 # in the use of the language that can be seen in all modules:
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9 #
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10 # * Except statements never specify target; instead, when needed,
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11 # the exception is taken from sys.exc_info(). Blame the incompatible
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12 # syntaxes of the except clause in Python 2.5 and Python 3 and the lack
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13 # of preprocessor macros in Python of any version ;P.
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14 #
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15 # * Keyword-only parameters are never used, even for parameters
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16 # that should never be given in as arguments. The reason is
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17 # the laziness of some Python developers who have failed to finish
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18 # implementing them in Python 2 even though they had several years
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19 # of time and multiple version releases to sneak them in.
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20 #
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21 # * Abstract classes are only implemented for Python 2.6 and 2.7.
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22 # ABC's require the abc module and the specification of metaclasses,
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23 # but in Python 2.5, the abc module does not exist, while in Python 3,
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24 # metaclasses are specified using a syntax totally incompatible
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25 # with Python 2 and not usable conditionally via exec() and such
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26 # because it is a detail of the syntax of the class statement itself.
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27
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28 __all__ = ('say', 'basestring', 'range', 'map', 'zip', 'filter',
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29 'items', 'keys', 'values', 'ABCMeta', 'abstractmethod')
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30
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31 try:
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32 # Python 3
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33 exec('say = print')
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34 except SyntaxError:
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35 try:
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36 # Python 2.6/2.7
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37 # An alternative is exec('from __future__ import print_function; say = print');
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38 # if problems arise with the current line, one should try replacing it
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39 # with this one with the future import before abandoning the idea altogether
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40 say = __builtins__['print']
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41 except Exception:
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42 # Python 2.5
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43 import sys
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44 # This should fully emulate the print function of Python 2.6 in Python 2.3+
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45 # The error messages are taken from Python 2.6
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46 # The name bindings at the bottom of this file are in effect
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47 def saytypeerror(value, name):
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48 return TypeError(' '.join((name, 'must be None, str or unicode, not', type(value).__name__)))
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49 def say(*values, **kwargs):
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50 sep = kwargs.pop('sep' , None)
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51 end = kwargs.pop('end' , None)
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52 file = kwargs.pop('file', None)
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53 if kwargs: raise TypeError("'%s' is an invalid keyword argument for this function" % kwargs.popitem()[0])
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54 if sep is None: sep = ' '
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55 if end is None: end = '\n'
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56 if file is None: file = sys.stdout
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57 if not isinstance(sep, basestring): raise saytypeerror(sep, 'sep')
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58 if not isinstance(end, basestring): raise saytypeerror(end, 'end')
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59 file.write(sep.join(map(str, values)) + end)
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60
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61 def import_urllib():
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62 try:
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63 # Python 3
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64 import urllib.request
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65 return urllib.request, lambda url: urllib.request.urlopen(url).read().decode()
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66 except ImportError:
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67 # Python 2
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68 import urllib
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69 return urllib, lambda url: urllib.urlopen(url).read()
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70
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71 try:
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72 from abc import ABCMeta, abstractmethod
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73 except ImportError:
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74 ABCMeta, abstractmethod = None, lambda x: x
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75
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76 # In all of the following, the try clause is for Python 2 and the except
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77 # clause is for Python 3. More checks are performed than needed
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78 # for standard builds of Python to ensure as much as possible works
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79 # on custom builds.
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80 try:
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81 basestring = basestring
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82 except NameError:
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83 basestring = str
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84
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85 try:
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86 range = xrange
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87 except NameError:
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88 range = range
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89
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90 try:
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91 from itertools import imap as map
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92 except ImportError:
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93 map = map
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94
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95 try:
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96 from itertools import izip as zip
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97 except ImportError:
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98 zip = zip
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99
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100 try:
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101 from itertools import ifilter as filter
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102 except ImportError:
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103 filter = filter
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104
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105 items = dict.iteritems if hasattr(dict, 'iteritems') else dict.items
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106 keys = dict.iterkeys if hasattr(dict, 'iterkeys') else dict.keys
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107 values = dict.itervalues if hasattr(dict, 'itervalues') else dict.values
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108
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109 for name in __all__:
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110 __builtins__[name] = globals()[name]
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111
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112 __builtins__['xrange'] = range |
