Python Programming Essentials - M28 - Debugging with pdb
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The document introduces the Python debugger (pdb) which allows developers to pause a Python program, examine variables, and step through code line-by-line or function-by-function. Pdb can be started from the command line using "python -m pdb filename" or by inserting "import pdb; pdb.set_trace()" in the code. The document describes common pdb commands like list, where, step, next, up and down that allow debugging and navigating the call stack.
Python Programming Essentials - M28 - Debugging with pdb
- 1. http://www.skillbrew.com /Skillbrew Talent brewed by the industry itself pdb – The interactive Debugger Pavan Verma @YinYangPavan Founder, P3 InfoTech Solutions Pvt. Ltd. 1 Python Programming Essentials
- 2. © SkillBrew http://skillbrew.com Content Python debugger introduction Enter into debugger via command line pdb commands 2
- 3. © SkillBrew http://skillbrew.com PDB - The Python Debugger 1. pdb implements an interactive debugging environment for Python programs 2. It lest you do a the following : 1. Pause your program 2. Look at the values of variables 3. Program execution step-by-step 4. Step up and down the call stack 3
- 4. © SkillBrew http://skillbrew.com Enter into Debugger via command line python –m pdb filename Running the debugger from the command line causes it to load your source file and stop execution on the first statement it finds 4
- 5. © SkillBrew http://skillbrew.com Enter into Debugger from within program (1) import pdb pdb.set_trace() Use pdb.set_trace()in the program where ever you want the program to enter into the debugger 5
- 6. © SkillBrew http://skillbrew.com pdb commands list or l Using list with a single numerical argument lists 11 lines around that line instead of the current line 6
- 7. © SkillBrew http://skillbrew.com pdb commands (2) where At any point while the debugger is running you can use where (abbreviated w) to find out exactly what line is being executed and where on the call stack you are 7
- 8. © SkillBrew http://skillbrew.com pdb commands (3) step Use step to execute the current line and then stop at the next execution point – either the first statement inside a function being called or the next line of the current function 8
- 9. © SkillBrew http://skillbrew.com pdb commands (4) next or n: The next command is like step, but does not enter functions called from the statement being executed. In effect, it steps all the way through the function call to the next statement in the current function in a single operation. 9
- 10. © SkillBrew http://skillbrew.com pdb commands (5) up (u) and down (d) • Move between frames within the current call stack using up and down • up (abbreviated u) moves towards older frames on the stack • down (abbreviated d) moves towards newer frames 10
- 11. © SkillBrew http://skillbrew.com Resources http://docs.python.org/2/library/pdb.html 11
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