文章目錄

• • 錯(cuò)誤處理
  • 調(diào)試
  • 單元測(cè)試unitcase
  • 文檔測(cè)試

1. 程序編寫問題bug – 字符類型錯(cuò)誤等
2. 用戶輸入錯(cuò)誤 – 輸入不符合規(guī)定的字符串
3. 異常，程序運(yùn)行時(shí)無(wú)法預(yù)測(cè) – 磁盤滿了，無(wú)法寫

錯(cuò)誤處理

錯(cuò)誤處理機(jī)制：try…except…finally…

1. try運(yùn)行可能會(huì)出錯(cuò)的代碼，若出錯(cuò)則后續(xù)代碼不再運(yùn)行
2. try中存在錯(cuò)誤代碼時(shí)，執(zhí)行except語(yǔ)句塊拋出異常
3. finally可有可無(wú)，不論是否異常，最后都會(huì)執(zhí)行
4. 所有錯(cuò)誤類型均繼承自BaseException
5. 不同except可以對(duì)不同錯(cuò)誤類型進(jìn)行處理
6. except可以捕獲自身及子類的錯(cuò)誤
7. except可以跨越多層調(diào)用

try:print('try...')test_int = 10 / int('a')				# 除法運(yùn)算錯(cuò)誤print('result = ', test_int)			# 由于上一行代碼錯(cuò)誤，try的后續(xù)代碼不再運(yùn)行
except ZeroDivisionError as e:		print('except: ', e)
except ValueError as e:print('ValueError:', e)
else：print('no error was found!')
finally:print('finally...')
print('END')

調(diào)用棧：出錯(cuò)時(shí)，須分析錯(cuò)誤的調(diào)用棧信息，以定位錯(cuò)誤的位置

Traceback (most recent call last):…………

logging模塊可以記錄錯(cuò)誤信息，且程序可繼續(xù)執(zhí)行

import logging
def foo(s):return 10 / int(s)
def bar(s):return foo(s) * 2
def main():try:bar('0')except Exception as e:logging.exception(e)
main()

輸出結(jié)果：

ERROR:root:division by zero
Traceback (most recent call last):File "/Pratice/DEMO.py", line 8, in mainbar('0')File "/Pratice/DEMO.py", line 5, in barreturn foo(s) * 2File "/Pratice/DEMO.py", line 3, in fooreturn 10 / int(s)
ZeroDivisionError: division by zero

raise拋出一個(gè)錯(cuò)誤的實(shí)例

def foo(s):n = int(s)if n==0:raise ValueError('invalid value: %s' % s)return 10 / ndef bar():try:foo('0')except ValueError as e:print('ValueError!')raisebar()

輸出結(jié)果：

Traceback (most recent call last):
ValueError!File "/Pratice/DEMO1.py", line 14, in <module>bar()File "/Pratice/DEMO1.py", line 9, in barfoo('0')File "/Pratice/DEMO1.py", line 4, in fooraise ValueError('invalid value: %s' % s)
ValueError: invalid value: 0

調(diào)試

使用print()調(diào)試，簡(jiǎn)單粗暴，但是調(diào)試過后需要?jiǎng)h除調(diào)試代碼

1. assert()斷言

def foo(s):n = int(s)assert n != 0, 'n is zero'	# 若‘n != 0’不成立，則拋出AssertionErrorreturn 10/sdef main():foo('0')
main()

	輸出結(jié)果：

Traceback (most recent call last):File "/Pratice/DEMO2.py", line 8, in <module>main()File "/Pratice/DEMO2.py", line 7, in mainfoo('0')File "/Pratice/DEMO2.py", line 3, in fooassert n != 0, 'n is zero'
AssertionError: n is zero

tips：python -O DEMO2.py 可以將DEMO2.py中的assert當(dāng)成pass來看
2. logging()記錄
輸出文件而不是拋出錯(cuò)誤
可指定記錄信息的級(jí)別
通過簡(jiǎn)單配置，一條語(yǔ)句可同時(shí)輸出到不同地方

import logging
# 指定記錄信息的級(jí)別 debug->info->warning->error
logging.basicConfig(level=logging.INFO)	s = '0'
n = int(s)
logging.info('n = %d' % n)
print(10 / n)

輸出結(jié)果：

INFO:root:n = 0
Traceback (most recent call last):File "/Pratice/DEMO3.py", line 7, in <module>print(10 / n)
ZeroDivisionError: division by zero

3. pdb調(diào)試器
   讓程序以單步方式運(yùn)行，隨時(shí)查看運(yùn)行狀態(tài)

?  python -m pdb DEMO.py	# 使用調(diào)試器查看單步運(yùn)行狀態(tài)
> /Users/amey/growingio/Pratice/DEMO.py(1)<module>()
-> import logging
(Pdb) l								# l查看代碼1  -> import logging2     logging.basicConfig(level=logging.INFO)3     4     s = '0'5     n = int(s)6     logging.info('n = %d' % n)7     print(10 / n)
[EOF]
(Pdb) n								# n -> 單步執(zhí)行代碼
> /Users/amey/growingio/Pratice/DEMO.py(2)<module>()
-> logging.basicConfig(level=logging.INFO)
(Pdb) n								# n -> 單步執(zhí)行代碼
> /Users/amey/growingio/Pratice/DEMO.py(4)<module>()
-> s = '0'
(Pdb) p s							# p 變量名 -> 查看變量
> '0'
(Pdb) q								# q -> 結(jié)束調(diào)試

單元測(cè)試unitcase

1. setUp()和tearDown()方法，在調(diào)用一個(gè)測(cè)試方法前后分別執(zhí)行
   [eg：連接關(guān)閉數(shù)據(jù)庫(kù)]
2. 使用python -m unittest test可以批量運(yùn)行多個(gè)單元測(cè)試

編寫一個(gè)學(xué)生成績(jī)單元測(cè)試

import unittestclass Student(object):def __init__(self, name ,score):self.name = nameself.score = scoredef get_grade(self):if(self.score > 100 or self.score < 0 or type(self.score) != int):raise ValueErrorelif(self.score < 60):return 'C'elif(self.score < 80):return 'B'else:return 'A'class TestStudent(unittest.TestCase):def test_80_to_100(self):s1 = Student('Amey', 100)s2 = Student('Jimmy', 80)self.assertEqual(s1.get_grade(),'A')self.assertEqual(s2.get_grade(),'A')def test_60_to_800(self):s1 = Student('Bart', 79)s2 = Student('Cindy', 60)self.assertEqual(s1.get_grade(),'B')self.assertEqual(s2.get_grade(),'B')def test_0_to_60(self):s1 = Student('Dan', 59)s2 = Student('Lisa', 0)self.assertEqual(s1.get_grade(),'C')self.assertEqual(s2.get_grade(),'C')def test_invaild(self):s1 = Student('Jan', 101)s2 = Student('King', -1)with self.assertRaises(ValueError):s1.get_grade()with self.assertRaises(ValueError):s2.get_grade()if __name__ == '__main__':unittest.main()

測(cè)試結(jié)果：

? python -m unittest DEMO4   
....
----------------------------------------------------------------------
Ran 4 tests in 0.000sOK

文檔測(cè)試

doctest模塊：可提取注視中的代碼并執(zhí)行測(cè)試

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
def fact(n):'''計(jì)算 1*2*3*...*n>>> fact(1)1>>> fact(-1)Traceback (most recent call last):File "/Pratice/demo.py", line 13, in <module>print(fact(-1))File "/Pratice/demo.py", line 7, in factraise ValueErrorValueError>>> fact(10)3628800'''if(n < 1):raise ValueErrorif(n == 1):return 1return n * fact(n-1)if __name__ == '__main__':import doctestdoctest.testmod()