[Dynamic Language] Python Debugger pdb

Python pdb 和 GNU gdb 一样容易上手,Module pdb 本身就包含了调式工具。

 abeen@localhost:~/learn_test/pdb$ cat test.py
#!/usr/bin/env python
# _*_ coding:utf-8 _*_

def testB(i):
    a ="abeen"
    b =1024
    x = b / i
    x +=1
    print x

def testA():
    testB(0)

def main():
    testA()

if__name__=="__main__":
    main()

运行调试

abeen@localhost:~/learn_test/pdb$ pdb test.py //启动调试
>/home/abeen/learn_test/pdb/test.py(4)<module>()
->def testB(i):
(Pdb) l //显示代码
  1#!/usr/bin/env python
2# _*_ coding:utf-8 _*_
3
  4->def testB(i):
  5         a ="abeen"
  6         b =1024
  7         x = b / i
  8         x +=1
  9print x
 10
 11def testA():
(Pdb) b 7//设置断点
Breakpoint 1 at /home/abeen/learn_test/pdb/test.py:7
(Pdb) b 8//设置断点
Breakpoint 2 at /home/abeen/learn_test/pdb/test.py:8
(Pdb) b //查看断点
Num Type         Disp Enb   Where
1   breakpoint   keep yes   at /home/abeen/learn_test/pdb/test.py:7
2   breakpoint   keep yes   at /home/abeen/learn_test/pdb/test.py:8
(Pdb) c
>/home/abeen/learn_test/pdb/test.py(7)testB()
-> x = b / i
(Pdb) p a,b,i
('abeen', 1024, 0)
(Pdb) w //查看调用
  /usr/lib/python2.6/bdb.py(368)run()
->exec cmd in globals, locals
  <string>(1)<module>()
  /home/abeen/learn_test/pdb/test.py(18)<module>()
-> main()
  /home/abeen/learn_test/pdb/test.py(15)main()
-> testA()
  /home/abeen/learn_test/pdb/test.py(12)testA()
-> testB(0)
>/home/abeen/learn_test/pdb/test.py(7)testB()
-> x = b / i

也可以在源代码中直接导入 pdb Module 进行调试。pdb.set_trace() 会启动 pdb 调试状态，可以是源代码的任何位置。

abeen@localhost:~/learn_test/pdb$ cat test.py
#!/usr/bin/env python
# _*_ coding:utf-8 _*_

def testB(i):
    a ="abeen"
    b =1024
    x = b / i
    x +=1
    print x

def testA():
    testB(0)

def main():
    testA()

if__name__=="__main__":
    import pdb
    pdb.set_trace()
    main()

pdb Module 中还提供了一些实用的函数，便于我们在 Python/iPython 交互模式下进行调试。

abeen@localhost:~/learn_test/pdb$ ipython
Python 2.6.5 (r265:79063, Apr 162010, 13:57:41)
In [1]: from test import*
In [2]: pycat te
test.py   test.pyc  testA     testB
In [2]: pycat test
#!/usr/bin/env python
# _*_ coding:utf-8 _*_

def testB(i):
    a ="abeen"
    b =1024
    x = b / i
    x +=1
    print x

def testA():
    testB(0)

def main():
    testA()

if__name__=="__main__":
    main()

In [3]: import pdb
In [5]: pdb.runcall(testB, 1)
>/home/abeen/learn_test/pdb/test.py(5)testB()
-> a ="abeen"
(Pdb) l
  1#!/usr/bin/env python
2# _*_ coding:utf-8 _*_
3
  4def testB(i):
  5->     a ="abeen"
  6         b =1024
  7         x = b / i
  8         x +=1
  9print x
 10
 11def testA():
(Pdb) b 5
Breakpoint 1 at /home/abeen/learn_test/pdb/test.py:5
(Pdb) b 7
Breakpoint 2 at /home/abeen/learn_test/pdb/test.py:7
(Pdb) b
Num Type         Disp Enb   Where
1   breakpoint   keep yes   at /home/abeen/learn_test/pdb/test.py:5
2   breakpoint   keep yes   at /home/abeen/learn_test/pdb/test.py:7 

另外一个需要关注的函数是 pdb.pm()，一旦程序出错发生未处理异常，它可以带我们去 "死亡现场" 查勘一番，类似 gdb core 或者 windbg dump。

In [10]: pfile testB
def testB(i):
    a ="abeen"
    b =1024
    x = b / i
    x +=1
    print x

def testA():
    testB(0)

def main():
    testA()

if__name__=="__main__":
    main()

In [11]: testB(0)
---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)

/home/abeen/learn_test/pdb/<ipython console>in<module>()

/home/abeen/learn_test/pdb/test.py in testB(i)
      5     a ="abeen"
      6     b =1024
---->7     x = b / i
      8     x +=1
      9print x

ZeroDivisionError: integer division or modulo by zero

In [12]: pdb.pm()
>/home/abeen/learn_test/pdb/test.py(7)testB()
-> x = b / i
(Pdb) w
  /usr/lib/pymodules/python2.6/IPython/iplib.py(2257)runcode()
->exec code_obj in self.user_global_ns, self.user_ns
  <ipython console>(1)<module>()
>/home/abeen/learn_test/pdb/test.py(7)testB()
-> x = b / i
(Pdb) l
  2# _*_ coding:utf-8 _*_
3
  4def testB(i):
  5         a ="abeen"
  6         b =1024
  7->     x = b / i
  8         x +=1
  9print x
 10
 11def testA():
 12         testB(0)
(Pdb) p a,b,i
('abeen', 1024, 0)
(Pdb)

pdb.pm() 实际调用的是 pdb.post_mortem() 函数，并将 sys.last_traceback 作为调用参数。其实在 iPython 里面我们直接设置 "%pdb ON" 就可以了，并不需要手工调用 pdb.pm()。

In [15]: %pdb 1
Automatic pdb calling has been turned ON

In [16]: testB(0)
---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)

/home/abeen/learn_test/pdb/<ipython console>in<module>()

/home/abeen/learn_test/pdb/test.py in testB(i)
      5     a ="abeen"
      6     b =1024
---->7     x = b / i
      8     x +=1
      9print x

ZeroDivisionError: integer division or modulo by zero
>/home/abeen/learn_test/pdb/test.py(7)testB()
      6     b =1024
---->7     x = b / i
      8     x +=1

 

 

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更多细节可参考：

 官方文档: 《26.2. pdb — The Python Debugger》
Python Conquers The Universe: 《Debugging in Python》
Jeremy Jones: 《Interactive Debugging in Python》