Dunes

"""
Example showing that attribute lookups always require consulting the class,
even if an attribute is found in the instance __dict__. This is due to data
descriptors taking prescedence over instance attributes.
"""
class DataDescriptor:
    def __get__(self, inst, cls=None):
        return 'descriptor'
    def __set__(self, inst, value):
        pass

Dunes

class MyContextManager:
    def __enter__(self):
        return self
    def __exit__(self, type_, value, traceback):
        # marks exception as being handled, and so it is not re-raised outside of the with block
        return True

with MyContextManager():
    raise ValueError
    data = None