Viewing file:  _compat.py (4.19 KB) -rw-r--r--
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from __future__ import absolute_import, division, print_function
import platform
import sys
import types
import warnings
PY2 = sys.version_info[0] == 2
PYPY = platform.python_implementation() == "PyPy"
if PY2:
from UserDict import IterableUserDict
# We 'bundle' isclass instead of using inspect as importing inspect is
# fairly expensive (order of 10-15 ms for a modern machine in 2016)
def isclass(klass):
return isinstance(klass, (type, types.ClassType))
# TYPE is used in exceptions, repr(int) is different on Python 2 and 3.
TYPE = "type"
def iteritems(d):
return d.iteritems()
# Python 2 is bereft of a read-only dict proxy, so we make one!
class ReadOnlyDict(IterableUserDict):
"""
Best-effort read-only dict wrapper.
"""
def __setitem__(self, key, val):
# We gently pretend we're a Python 3 mappingproxy.
raise TypeError("'mappingproxy' object does not support item "
"assignment")
def update(self, _):
# We gently pretend we're a Python 3 mappingproxy.
raise AttributeError("'mappingproxy' object has no attribute "
"'update'")
def __delitem__(self, _):
# We gently pretend we're a Python 3 mappingproxy.
raise TypeError("'mappingproxy' object does not support item "
"deletion")
def clear(self):
# We gently pretend we're a Python 3 mappingproxy.
raise AttributeError("'mappingproxy' object has no attribute "
"'clear'")
def pop(self, key, default=None):
# We gently pretend we're a Python 3 mappingproxy.
raise AttributeError("'mappingproxy' object has no attribute "
"'pop'")
def popitem(self):
# We gently pretend we're a Python 3 mappingproxy.
raise AttributeError("'mappingproxy' object has no attribute "
"'popitem'")
def setdefault(self, key, default=None):
# We gently pretend we're a Python 3 mappingproxy.
raise AttributeError("'mappingproxy' object has no attribute "
"'setdefault'")
def __repr__(self):
# Override to be identical to the Python 3 version.
return "mappingproxy(" + repr(self.data) + ")"
def metadata_proxy(d):
res = ReadOnlyDict()
res.data.update(d) # We blocked update, so we have to do it like this.
return res
else:
def isclass(klass):
return isinstance(klass, type)
TYPE = "class"
def iteritems(d):
return d.items()
def metadata_proxy(d):
return types.MappingProxyType(dict(d))
def import_ctypes(): # pragma: nocover
"""
Moved into a function for testability.
"""
try:
import ctypes
return ctypes
except ImportError:
return None
if not PY2:
def just_warn(*args, **kw):
"""
We only warn on Python 3 because we are not aware of any concrete
consequences of not setting the cell on Python 2.
"""
warnings.warn(
"Missing ctypes. Some features like bare super() or accessing "
"__class__ will not work with slots classes.",
RuntimeWarning,
stacklevel=2,
)
else:
def just_warn(*args, **kw): # pragma: nocover
"""
We only warn on Python 3 because we are not aware of any concrete
consequences of not setting the cell on Python 2.
"""
def make_set_closure_cell():
"""
Moved into a function for testability.
"""
if PYPY: # pragma: no cover
def set_closure_cell(cell, value):
cell.__setstate__((value,))
else:
ctypes = import_ctypes()
if ctypes is not None:
set_closure_cell = ctypes.pythonapi.PyCell_Set
set_closure_cell.argtypes = (ctypes.py_object, ctypes.py_object)
set_closure_cell.restype = ctypes.c_int
else:
set_closure_cell = just_warn
return set_closure_cell
set_closure_cell = make_set_closure_cell()
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