#!/usr/bin/python2.4
# An exception handling idiom using decorators.
__author__ = "Anand Pillai"
def ExpHandler(*posargs):
def nestedhandler(func,exptuple, *pargs, **kwargs):
""" Function that creates a nested exception handler from
the passed exception tuple """
exp, handler = exptuple[0]
try:
if len(exptuple)==1:
func(*pargs, **kwargs)
else:
nestedhandler(func,exptuple[1:], *pargs, **kwargs)
except exp, e:
if handler:
handler(e)
else:
print e.__class__.__name__,':',e
def wrapper(f):
def newfunc(*pargs, **kwargs):
if len(posargs)<2:
t = tuple(item for item in posargs[0] if issubclass(item,Exception) or (Exception,))
try:
f(*pargs, **kwargs)
except t, e:
print e.__class__.__name__,':',e
else:
t1, t2 =posargs[0], posargs[1]
l=[]
for x in xrange(len(t1)):
try:
l.append((t1[x],t2[x]))
except:
l.append((t1[x],None))
# Reverse list so that exceptions will
# be caught in order.
l.reverse()
t = tuple(l)
nestedhandler(f,t,*pargs,**kwargs)
return newfunc
return wrapper
def myhandler(e):
print 'Caught exception!', e
# Examples
# Specify exceptions in order, first one is handled first
# last one last.
@ExpHandler((ZeroDivisionError,ValueError), (None,myhandler))
def f1():
1/0
@ExpHandler((TypeError, ValueError, StandardError), (myhandler,)*3)
def f2(*pargs, **kwargs):
print pargs
x = pargs[0]
y = x[0]
y += x[1]
@ExpHandler((ValueError, Exception))
def f3(*pargs):
l = pargs[0]
return l.index(10)
if __name__=="__main__":
f1()
# Calls exception handler
f2('Python', 1)
# Calls exception handler
f3(range(5),)
