使用PDB調試Python程式

 

本文討論在沒有方便的IDE工具可用的情況下，使用pdb調試python程式 源碼例子例如，有類比稅收計算的程式： #!/usr/bin/python  def debug_demo(val):                  if val <= 1600 :                                  print "level 1"                                  print 0                  elif val <= 3500 :                                  print "level 2"                                  print (val - 1600) * 0.05                  elif val <= 6500 :                                  print "level 3"                                  print (val - 3500) * 0.10 + (3500-1600) * 0.05                  else:                                  print "level 4"                                  print (val - 6500) * 0.20 + (6500-3500) * 0.10 + (3500-1600) * 0.05                                    #~def debug_demo                                    if __name__ == "__main__":                                    debug_demo(4500)  debug_demoFunction Compute4500的入賬所需的稅收。 如何調試? 1.加入斷點 在需要插入斷點的地方，加入紅色部分代碼：如果_DEBUG值為True，則在該處開始調試（加入_DEBUG的原因是為了方便開啟/關閉調試）。 #!/usr/bin/python  _DEBUG=True  def debug_demo(val):                  if _DEBUG == True:                                  import pdb                                  pdb.set_trace()                  if val <= 1600 :                                  print "level 1"                                  print 0                  elif val <= 3500 :                                  print "level 2"                                  print (val - 1600) * 0.05                  elif val <= 6500 :                                  print "level 3"                                  print (val - 3500) * 0.10 + (3500-1600) * 0.05                  else:                                  print "level 4"                                  print (val - 6500) * 0.20 + (6500-3500) * 0.10 + (3500-1600) * 0.05  #~def debug_demo                  if __name__ == "__main__":                  debug_demo(4500)    2.開始運行調試   運行程式./debug_demo.py,得到 > /usr/local/qspace/user_network/debug_demo.py(7)debug_demo()  -> if val <= 1600 :  (Pdb)-> val <= 1600 : 指示當前執行的語句，（Pdb）等待你的調試指令. pdb的指令很豐富，輸入h指令可以查看指令的使用方法。下面簡單介紹常用指令：    查看代碼上下文，l（小寫L） (Pdb) l      2         _DEBUG=True      3         def debug_demo(val):      4                         if _DEBUG == True:      5                                         import pdb      6                                         pdb.set_trace()      7    ->                 if val <= 1600 :      8                                         print "level 1"      9                                         print 0  10                         elif val <= 3500 :  11                                         print "level 2"  12                                         print (val - 1600) * 0.05  (Pdb)     左邊是行號，右邊是代碼本文。   監視變數：p 變數名 (Pdb) p val  4500  (Pdb)      逐步執行: n -> elif val <= 3500 :  (Pdb) l      5                                         import pdb      6                                         pdb.set_trace()      7                         if val <= 1600 :      8                                         print "level 1"      9                                         print 0  10    ->                 elif val <= 3500 :  11                                         print "level 2"  12                                         print (val - 1600) * 0.05  13                         elif val <= 6500 :  14                                         print "level 3"  15                                         print (val - 3500) * 0.10 + (3500-1600) * 0.05   加入斷點:b 行號 (Pdb) b 14  運行到斷點: c (Pdb) c  > /*****  -> print "level 3"  (Pdb) l      9                                         print 0  10                         elif val <= 3500 :  11                                         print "level 2"  12                                         print (val - 1600) * 0.05  13                         elif val <= 6500 :  14 B->                                 print "level 3"  15                                         print (val - 3500) * 0.10 + (3500-1600) * 0.05  16                         else:  17                                         print "level 4"  18                                         print (val - 6500) * 0.20 + (6500-3500) * 0.10 + (3500-1600) * 0.05  19      執行到函數返回前: r (Pdb) r  level 3  195.0  --Return--  > /****()->None  -> print (val - 3500) * 0.10 + (3500-1600) * 0.05  (Pdb)     說明：  pdb還有很多其他很多有用的指令，讀者可以自行探索。輸入h，h 命令。就可以得到命令的詳細協助。  不過，我個人認為一般無需啟動這種調試方法，一般使用日誌輸出進行調試即可，除非遇到了非常微妙的錯誤。這時，單步調試的威力便顯示出來了。

 

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