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Add some tests for ways users can change or shadow globals and builtins.

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This commit is contained in:
Collin Winter 2010-03-17 00:41:56 +00:00
parent 0077b65a9e
commit f2bf2b3ec4
2 changed files with 199 additions and 1 deletions
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57
Lib/test/support.py
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@ -30,7 +30,8 @@ __all__ = ["Error", "TestFailed", "ResourceDenied", "import_module",
"run_with_locale",
"set_memlimit", "bigmemtest", "bigaddrspacetest", "BasicTestRunner",
"run_unittest", "run_doctest", "threading_setup", "threading_cleanup",
"reap_children", "cpython_only", "check_impl_detail", "get_attribute"]
"reap_children", "cpython_only", "check_impl_detail", "get_attribute",
"swap_item", "swap_attr"]
class Error(Exception):
"""Base class for regression test exceptions."""
@ -1074,3 +1075,57 @@ def reap_children():
break
except:
break
@contextlib.contextmanager
def swap_attr(obj, attr, new_val):
"""Temporary swap out an attribute with a new object.
Usage:
with swap_attr(obj, "attr", 5):
...
This will set obj.attr to 5 for the duration of the with: block,
restoring the old value at the end of the block. If `attr` doesn't
exist on `obj`, it will be created and then deleted at the end of the
block.
"""
if hasattr(obj, attr):
real_val = getattr(obj, attr)
setattr(obj, attr, new_val)
try:
yield
finally:
setattr(obj, attr, real_val)
else:
setattr(obj, attr, new_val)
try:
yield
finally:
delattr(obj, attr)
@contextlib.contextmanager
def swap_item(obj, item, new_val):
"""Temporary swap out an item with a new object.
Usage:
with swap_item(obj, "item", 5):
...
This will set obj["item"] to 5 for the duration of the with: block,
restoring the old value at the end of the block. If `item` doesn't
exist on `obj`, it will be created and then deleted at the end of the
block.
"""
if item in obj:
real_val = obj[item]
obj[item] = new_val
try:
yield
finally:
obj[item] = real_val
else:
obj[item] = new_val
try:
yield
finally:
del obj[item]