This module provides mechanisms to use signal handlers in
Python. Some general rules for working with signals and their
handlers: - A handler for a particular signal, once set, remains
installed until it is explicitly reset (Python emulates the BSD
style interface regardless of the underlying implementation),
with the exception of the handler for SIGCHLD, which follows the
underlying - There is no way to ``block'' signals temporarily
from critical sections (since this is not supported by all Unix
flavors). - Although Python signal handlers are called
asynchronously as far as the Python user is concerned, they can
only occur between the ``atomic'' instructions of the Python
interpreter. This means that signals arriving during long
calculations implemented purely in C (such as regular expression
matches on large bodies of text) may be delayed for an arbitrary
amount of time. - When a signal arrives during an I/O operation,
it is possible that the I/O operation raises an exception after
the signal handler return