python總結（十三） 錯誤與除錯

1、處理錯誤：

try:

print('try...')
r = 10 / int('2')
print('result:', r)
except exception as e:
print('valueerror:', e)
except zerodivisionerror as e:
print('zerodivisionerror:', e)
else:
"""當沒有錯誤發生時，會自動執行else語句："""
print('no error!')
finally:
print('finally...')
print('end')

try:

10 / 0
except zerodivisionerror:
raise valueerror('input error!')

# err_raise.py

class fooerror(valueerror):
pass
def foo(s):
n = int(s)
if n==0:
raise fooerror('invalid value: %s' % s)
return 10 / n
foo('0')

def foo(s):

n = int(s)
print('>>> n = %d' % n)
return 10 / n
def main():
foo('0')
main()

def foo(s):

n = int(s)
assert n != 0, 'n is zero!'
return 10 / n
def main():
foo('0')
"""斷言錯誤的輸出"""
"""traceback (most recent call last):
file "c:/users/lenovo/pycharmprojects/matplot_graph/venv/classtext.py", line 7, in main()
file "c:/users/lenovo/pycharmprojects/matplot_graph/venv/classtext.py", line 6, in main
foo('0')
file "c:/users/lenovo/pycharmprojects/matplot_graph/venv/classtext.py", line 3, in foo
assert n != 0, 'n is zero!'
assertionerror: n is zero!
"""

程式中如果到處充斥著assert，和print()相比也好不到哪去.啟動python直譯器時可以用-o（大寫字母）引數來關閉assert。

$ python -o err.py

traceback (most recent call last):
...zerodivisionerror: division by zero

（1）啟動：

python -m pdb err.py

（2）輸入命令l來檢視**

（3）輸入命令n可以單步執行**

（4）任何時候都可以輸入命令p 變數名來檢視變數

（5）輸入命令q結束除錯，退出程式 

(6) c 繼續執行

import pdb

pdb.set_trace()

import unittest

from dict import dict
class testdict(unittest.testcase):
def test_init(self):
d = dict(a=1, b='test')
"""測試的類名"""
self.assertequal(d.a, 1)
self.assertequal(d.b, 'test')
self.asserttrue(isinstance(d, dict))
def test_key(self):
d = dict()
d['key'] = 'value'
self.assertequal(d.key, 'value')
def test_attr(self):
d = dict()
d.key = 'value'
self.asserttrue('key' in d)
self.assertequal(d['key'], 'value')
def test_keyerror(self):
d = dict()
with self.assertraises(keyerror):
value = d['empty']
def test_attrerror(self):
d = dict()
with self.assertraises(attributeerror):
value = d.empty
def setup(self):
print('setup...')
def teardown(self):
print('teardown...')

python -m unittest mydict_test

當然，引數是可變的：

python -m unittest mydict_test mytest

可以執行無限多個測試類

class dict(dict):

'''****** dict but also support access as x.y style.
>>> d1 = dict()
>>> d1['x'] = 100
>>> d1.x
100>>> 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.empty
traceback (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] = value
if __name__=='__main__':
import doctest
doctest.testmod()

python mydice2.py

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