# err.py:
def foo(s):return 10 / int(s)def bar(s):return foo(s) * 2def main():bar('0')main()

$ python err.py
Traceback (most recent call last):File "err.py", line 11, in <module>main()File "err.py", line 9, in mainbar('0')File "err.py", line 6, in barreturn foo(s) * 2File "err.py", line 3, in fooreturn 10 / int(s)
ZeroDivisionError: integer division or modulo by zero

try:print 'try...'r = 10 / 0print 'result:', r
except ZeroDivisionError, e:print 'except:', e
finally:print 'finally...'
print 'END'

try...
except: integer division or modulo by zero
finally...
END

# err.py
def foo(s):n = int(s)assert n != 0, 'n is zero!'return 10 / ndef main():foo('0')

# err.py
import logginglogging.basicConfig(level=logging.INFO)s = '0'
n = int(s)
logging.info('n = %d' % n)
print 10 / n

$ python err.py
INFO:root:n = 0
Traceback (most recent call last):File "err.py", line 8, in <module>print 10 / n
ZeroDivisionError: integer division or modulo by zero

# err.py
s = '0'
n = int(s)
print 10 / n

$ python -m pdb err.py
> /Users/michael/Github/sicp/err.py(2)<module>()
-> s = '0'

(Pdb) l1     # err.py2  -> s = '0'3     n = int(s)4     print 10 / n
[EOF]

(Pdb) n
> /Users/michael/Github/sicp/err.py(3)<module>()
-> n = int(s)
(Pdb) n
> /Users/michael/Github/sicp/err.py(4)<module>()
-> print 10 / n

(Pdb) p s
'0'
(Pdb) p n
0

(Pdb) n
ZeroDivisionError: 'integer division or modulo by zero'
> /Users/michael/Github/sicp/err.py(4)<module>()
-> print 10 / n
(Pdb) q

# err.py
import pdbs = '0'
n = int(s)
pdb.set_trace() # 运行到这里会自动暂停
print 10 / n

$ python err.py
> /Users/michael/Github/sicp/err.py(7)<module>()
-> print 10 / n
(Pdb) p n
0
(Pdb) c
Traceback (most recent call last):File "err.py", line 7, in <module>print 10 / n
ZeroDivisionError: integer division or modulo by zero

>>> d = Dict(a=1, b=2)
>>> d['a']
1
>>> d.a
1

class Dict(dict):def __init__(self, **kw):super(Dict, self).__init__(**kw)def __getattr__(self, key):try:return self[key]except KeyError:raise AttributeError(r"'Dict' object has no attribute '%s'" % key)def __setattr__(self, key, value):self[key] = value

import unittestfrom mydict import Dictclass TestDict(unittest.TestCase):def test_init(self):　　# 测试初始化功能d = Dict(a=1, b='test')self.assertEquals(d.a, 1)self.assertEquals(d.b, 'test')self.assertTrue(isinstance(d, dict))def test_key(self):　　# 测试key的功能d = Dict()d['key'] = 'value'self.assertEquals(d.key, 'value')def test_attr(self):　　# 测试属性功能d = Dict()d.key = 'value'self.assertTrue('key' in d)self.assertEquals(d['key'], 'value')def test_keyerror(self):　　# 测试key错误的功能d = Dict()with self.assertRaises(KeyError):value = d['empty']def test_attrerror(self):　　# 测试属性错误的功能d = Dict()with self.assertRaises(AttributeError):value = d.empty

if __name__ == '__main__':unittest.main()

$ python -m unittest mydict_test
.....
----------------------------------------------------------------------
Ran 5 tests in 0.000sOK

class Dict(dict):'''Simple dict but also support access as x.y style.>>> d1 = Dict()>>> d1['x'] = 100>>> d1.x100>>> d1.y = 200>>> d1['y']200>>> d2 = Dict(a=1, b=2, c='3')>>> d2.c'3'>>> d2['empty']Traceback (most recent call last):...KeyError: 'empty'>>> d2.emptyTraceback (most recent call last):...AttributeError: 'Dict' object has no attribute 'empty''''def __init__(self, **kw):super(Dict, self).__init__(**kw)def __getattr__(self, key):try:return self[key]except KeyError:raise AttributeError(r"'Dict' object has no attribute '%s'" % key)def __setattr__(self, key, value):self[key] = valueif __name__=='__main__':import doctestdoctest.testmod()