使用Python調(diào)試器（pdb）能有效排查問(wèn)題，首先通過(guò)在代碼中插入breakpoint()函數(shù)啟動(dòng)調(diào)試，程序運(yùn)行到該處會(huì)自動(dòng)暫停並進(jìn)入交互式調(diào)試環(huán)境；其次掌握常用命令：1. n（執(zhí)行當(dāng)前行並移動(dòng)到下一行）2. s（進(jìn)入函數(shù)內(nèi)部）3. c（繼續(xù)執(zhí)行直到下一個(gè)斷點(diǎn)）4. l（顯示當(dāng)前代碼上下文）5. p 變量名（打印變量值）6. pp 表達(dá)式（美化輸出複雜數(shù)據(jù)結(jié)構(gòu)）7. r（運(yùn)行至當(dāng)前函數(shù)返回）8. w（顯示調(diào)用棧）9. q（退出調(diào)試器）；可通過(guò)python -m pdb my_script.py從命令行啟動(dòng)調(diào)試，並用b命令設(shè)置行或函數(shù)斷點(diǎn)；建議避免在生產(chǎn)代碼中保留breakpoint()，可設(shè)置PYTHONBREAKPOINT=0禁用，結(jié)合pp locals()查看局部變量，推薦使用ipdb等增強(qiáng)工具提升調(diào)試體驗(yàn)，pdb雖簡(jiǎn)潔但功能可靠且內(nèi)置於Python中。

Using the Python debugger (pdb) is a powerful way to step through your code, inspect variables, and understand program flow when things go wrong. Here's how to use it effectively.

Starting pdb

The easiest way to start using pdb is by inserting a breakpoint in your code. In Python 3.7 , you can use the built-in breakpoint() function:

 def my_function():
    x = 10
    y = 20
    breakpoint() # Execution will pause here
    z = xy
    return z

my_function()

When the program reaches breakpoint() , it will pause and drop into the interactive debugger.

Note: breakpoint() is equivalent to import pdb; pdb.set_trace() but is preferred because it respects environment variables like PYTHONBREAKPOINT and can be disabled globally.

If you're using an older version of Python, use:

 import pdb; pdb.set_trace()

Common pdb Commands

Once inside the debugger, you'll see a (Pdb) prompt. Here are the most useful commands:

• n (next) : Execute the current line and move to the next line in the current function.
• s (step) : Step into a function call. If the current line calls a function, s will enter it.
• c (continue) : Continue execution until a breakpoint is hit or the program ends.
• l (list) : Show the current code around the current line.
• p variable_name (print) : Print the value of a variable. For example: px .
• pp expression : Pretty-print the result of an expression (useful for dicts, lists).
• r (return) : Continue execution until the current function returns.
• w (where) : Show the current stack trace (where you are in the call stack).
• q (quit) : Exit the debugger and stop the program.

Example:

 def add(a, b):
    return ab

def main():
    x = 5
    y = 10
    breakpoint()
    result = add(x, y)
    print(result)

main()

At the breakpoint, you can:

 (Pdb) px
5
(Pdb) py
10
(Pdb) s
--Call--
> <stdin>(1)add()

You stepped into the add function.

Using pdb from the Command Line

You can also run a script under pdb directly from the terminal:

 python -m pdb my_script.py

This starts the debugger before running the script. Use c to run until the first breakpoint or l to list code.

When launched this way, execution doesn't stop until it hits a breakpoint() or you use the b (break) command to set breakpoints.

Setting Breakpoints in Code

You can set breakpoints at specific lines or functions:

 import pdb

pdb.set_trace() # Break here

Or set conditional breakpoints:

 if some_condition:
    import pdb; pdb.set_trace()

You can also use the b command in the debugger to set future breakpoints:

• b 10 – set a breakpoint at line 10
• b my_function – set a breakpoint at the start of my_function
• b myfile.py:20 – set a breakpoint in another file

Tips and Best Practices

• Use pp locals() to see all local variables in a readable format.
• Avoid leaving breakpoint() calls in production code. You can disable them with PYTHONBREAKPOINT=0 :

   PYTHONBREAKPOINT=0 python my_script.py

• Combine pdb with logging for non-interactive debugging.
• Consider using enhanced debuggers like ipdb (with IPython) for better syntax highlighting and tab completion.

Basically, pdb gives you control to pause, inspect, and step through your code. It's not flashy, but it's reliable and built into Python.

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