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34397
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1 from __future__ import absolute_import, division, print_function
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2
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3 import sys
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4 import types
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5
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6
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7 PY2 = sys.version_info[0] == 2
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8
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9
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10 if PY2:
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11 from UserDict import IterableUserDict
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12
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13 # We 'bundle' isclass instead of using inspect as importing inspect is
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14 # fairly expensive (order of 10-15 ms for a modern machine in 2016)
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15 def isclass(klass):
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16 return isinstance(klass, (type, types.ClassType))
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17
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18 # TYPE is used in exceptions, repr(int) is different on Python 2 and 3.
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19 TYPE = "type"
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20
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21 def iteritems(d):
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22 return d.iteritems()
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23
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24 def iterkeys(d):
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25 return d.iterkeys()
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26
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27 # Python 2 is bereft of a read-only dict proxy, so we make one!
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28 class ReadOnlyDict(IterableUserDict):
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29 """
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30 Best-effort read-only dict wrapper.
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31 """
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32
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33 def __setitem__(self, key, val):
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34 # We gently pretend we're a Python 3 mappingproxy.
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35 raise TypeError("'mappingproxy' object does not support item "
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36 "assignment")
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37
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38 def update(self, _):
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39 # We gently pretend we're a Python 3 mappingproxy.
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40 raise AttributeError("'mappingproxy' object has no attribute "
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41 "'update'")
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42
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43 def __delitem__(self, _):
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44 # We gently pretend we're a Python 3 mappingproxy.
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45 raise TypeError("'mappingproxy' object does not support item "
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46 "deletion")
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47
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48 def clear(self):
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49 # We gently pretend we're a Python 3 mappingproxy.
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50 raise AttributeError("'mappingproxy' object has no attribute "
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51 "'clear'")
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52
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53 def pop(self, key, default=None):
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54 # We gently pretend we're a Python 3 mappingproxy.
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55 raise AttributeError("'mappingproxy' object has no attribute "
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56 "'pop'")
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57
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58 def popitem(self):
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59 # We gently pretend we're a Python 3 mappingproxy.
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60 raise AttributeError("'mappingproxy' object has no attribute "
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61 "'popitem'")
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62
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63 def setdefault(self, key, default=None):
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64 # We gently pretend we're a Python 3 mappingproxy.
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65 raise AttributeError("'mappingproxy' object has no attribute "
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66 "'setdefault'")
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67
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68 def __repr__(self):
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69 # Override to be identical to the Python 3 version.
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70 return "mappingproxy(" + repr(self.data) + ")"
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71
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72 def metadata_proxy(d):
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73 res = ReadOnlyDict()
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74 res.data.update(d) # We blocked update, so we have to do it like this.
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75 return res
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76
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77 else:
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78 def isclass(klass):
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79 return isinstance(klass, type)
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80
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81 TYPE = "class"
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82
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83 def iteritems(d):
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84 return d.items()
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85
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86 def iterkeys(d):
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87 return d.keys()
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88
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89 def metadata_proxy(d):
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90 return types.MappingProxyType(dict(d))
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