Python 调试，,1.1调试1.1.1

Python 调试，,1.1调试1.1.1

1.1调试

1.1.1print()

在shell和plsql中我都习惯用echo和dbms_output.put_line输出变量，查看变量异常。

在python程序中，可用print()函数展示变量。

缺点就是，调试完成后，需编辑源代码删除多余的print函数。

这里不做实例演示。

1.1.2assert

凡是可用print()函数来查看的地方，都可用assert。

>>> def foo(s):

...n = int(s)

...assert n != 0, ‘n is zero.‘ -- n != 0为真，继续往下运行，否则抛出字符串异常

...return 10 / n

...

>>> def main():

...foo(‘0‘)

...

>>> main()

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

File "<stdin>", line 2, in main

File "<stdin>", line 3, in foo

AssertionError: n is zero.

启动Python解释器时可以用-O参数（大写字母O）来关闭assert。

例如python -O assert.py

[[email protected] python]# cat assert.py

#!/usr/bin/python

# -*- coding:utf-8 -*-

def foo(s):

n= int(s)

assert n != 0, ‘n is zero!‘

return 10 / n

def main():

foo(‘0‘)

main()

[[email protected] python]# python -O assert.py

Traceback (most recent call last):

File "assert.py", line 11, in <module>

main()

File "assert.py", line 9, in main

foo(‘0‘)

File "assert.py", line 6, in foo

return 10 / n

ZeroDivisionError: division by zero

关闭之后所有assert语句等价于pass

1.1.3logging

可以简单理解logging为记录的意思，logging不会抛出错误。

[[email protected] python]# cat err_log_level.py

import logging

logging.basicConfig(level=logging.INFO)

s = ‘1‘

n = int(s)

logging.info(‘n = %d‘ %n)

print(10 / n)

[[email protected] python]# pythonerr_log_level.py

INFO:root:n = 1 -- logging.info输出后面的信息

10.0

[[email protected] python]# cat err_log_level.py

import logging

logging.basicConfig(level=logging.INFO)

s = ‘0‘

n = int(s)

logging.info(‘n = %d‘ %n)

print(10 / n)

[[email protected] python]# pythonerr_log_level.py

INFO:root:n = 0

Traceback (most recent call last):

File "err_log_level.py", line 6, in <module>

print(10 / n)

ZeroDivisionError: division by zero

logging无论有没有错误抛出，都会输出记录。

指定记录信息的级别：debug，info，warning，error

1.1.4pdb

启动Python的调试器pdb，让程序以单步方式运行，可以随时查看运行状态。

[[email protected] python]# python -m pdb err.py--启用pdb

> /root/python/err.py(4)<module>()

-> def foo(s):

(Pdb) l

1 #!/bin/bash/python

2 # -*- coding:utf-8 -*-

3

4 -> def foo(s):

5 return 10 / int(s)

6

7 def bar(s):

8 return foo(s) * 2

9

10def main():

11bar(‘0‘)

(Pdb) n

> /root/python/err.py(7)<module>()

-> def bar(s):

(Pdb) l

2 # -*- coding:utf-8 -*-

3

4 def foo(s):

5 return 10 / int(s)

6

7 -> def bar(s):

8 return foo(s) * 2

9

10def main():

11bar(‘0‘)

12

(Pdb) n

>/root/python/err.py(10)<module>()

-> def main():

(Pdb) l

5 return 10 / int(s)

6

7 def bar(s):

8 return foo(s) * 2

9

10-> def main():

11bar(‘0‘)

12

13main()

14

[EOF]

(Pdb) n

>/root/python/err.py(13)<module>()

-> main()

(Pdb) l

8 return foo(s) * 2

9

10def main():

11bar(‘0‘)

12

13-> main()

14

[EOF]

(Pdb) n

ZeroDivisionError: division by zero

> /root/python/err.py(13)<module>()

-> main()

(Pdb)

交互式命令说明：

l：查看代码；

n：执行下一步；

p：查看变量，p 变量名；

q：退出pdb。

1.1.5pdb.set_trace()

这种方法也是调用pdb，只是不需单步调用，相当于断点。

[[email protected] python]# cat err.py

#!/bin/bash/python

# -*- coding:utf-8 -*-

import pdb

def foo(s):

return 10 / int(s)

pdb.set_trace()

def bar(s):

return foo(s) * 2

pdb.set_trace()

def main():

bar(‘0‘)

pdb.set_trace()

main()

[[email protected] python]# python err.py

> /root/python/err.py(9)<module>()

-> def bar(s):

(Pdb) l

4 import pdb

5

6 def foo(s):

7return 10 / int(s)

8 pdb.set_trace() --遇到第一个断点程序就停止运行

9 -> def bar(s):

10return foo(s) * 2

11pdb.set_trace()

12def main():

13bar(‘0‘)

14pdb.set_trace()

(Pdb) n

> /root/python/err.py(11)<module>()

-> pdb.set_trace()

(Pdb) p s

*** NameError: name ‘s‘ is not defined

(Pdb) n

>/root/python/err.py(12)<module>()

-> def main():

(Pdb) n

>/root/python/err.py(14)<module>()

-> pdb.set_trace()

(Pdb) l

9 def bar(s):

10return foo(s) * 2

11 pdb.set_trace()

12def main():

13bar(‘0‘)

14-> pdb.set_trace()

15main()

16

[EOF]

(Pdb) n

>/root/python/err.py(15)<module>()

-> main()

(Pdb) n

ZeroDivisionError: division by zero

>/root/python/err.py(15)<module>()

-> main()

在调试过程中，逐步改变断点的位置，从而缩小错误的范围。

1.1.6终极武器

难道logging才是调试代码的终极武器，待议。

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Python 调试