1. Preparation before debugging
1. Prepare a test code
First write a simple Python script (such as calculating factorials) and deliberately leave some questions:
def factorial(n):
result = 1
for i in range(n):
result *= i
return result
print(factorial(5)) # Expected output120，But the actual output0？2. Why is debugging required?
- When the code runs the result not in the expectations, debugging can help you track the code execution process line by line.
- You can view the changes in the variable value and find out logical errors.
2. Debugging core operations (with screenshot steps)
1. Setting Breakpoint
- Function: Let the program be paused when it runs here for easy observation.
- Operation: Click on the left side of the code line number, and a red dot appears.
- (Example: on line 3
result = 1and line 5result *= iSet breakpoints)
2. Start debug mode
- Method 1: Click the green beetle icon in the upper right corner 🐞.
- Method 2: Right-click code → Select
Debug 'file name'。
3. Debug interface layout
After starting debugging, PyCharm will automatically enter the debug view, which is mainly divided into:
- ① Debug toolbar: Control code execution (step, recovery, etc.).
- ② Variables: Displays the variable value in the current scope.
- ③Console: Display program output and input.
3. Detailed explanation of key debug buttons
| Button Icon | name | shortcut key | Description of function |
|---|---|---|---|
| ▶️ | Resume | F9 | Continue to execute the program until the next breakpoint or end. |
| ➡️ | Step Over | F8 | Execute the current line of code without entering the function or loop inside. |
| ⬇️ | Step Into | F7 | Execute the current line of code and enter the function inside (such as when debugging custom functions). |
| ⬆️ | Step Out | Shift+F8 | Jump out from inside the current function and return to where it was called. |
| 🛑 | Stop | Ctrl+F2 | Terminate the debugging process. |
4. Actual debugging process (taking the example code as an example)
1. First pause (breakpoint: line 3)
- Observe the variable window: At this time
n=5，result=1(correct). - Click
Step Over（F8）: Executeresult = 1。
2. Enter the loop (breakpoint: line 5)
ClickStep Over(F8) Multiple times, observe each cycleiandresultChanges:
- Problem exposed: During the first cycle
i=0,lead toresult *= 0, the result becomes 0! - Error Cause：
range(n)What is generated is[0,1,2,3,4], should1Start the loop.
3. Repair the code
Modify the loop range:for i in range(1, n+1):
5. Advanced debugging skills
1. Conditional Breakpoint
- Function: Pause when a specific condition is met.
- Settings: Right-click the breakpoint → Enter the condition (such as
i == 3）。
2. Monitoring expressions (Watches)
- Function: Monitor the value of a variable or expression in real time.
- Operation: At
WatchesWindow click+→ Enter expression (egi * 2）。
3. Rerun debugging
- After modifying the code, you do not need to close debugging, just click the debug button to restart.
6. Troubleshooting of FAQs
1. The program is not paused during debugging?
- Check if a breakpoint is set.
- Make sure the code is indeed executed to the breakpoint position.
2. The variable window does not display the value?
- Confirm that the program has been paused at the breakpoint.
- Check whether the variable is within the current scope (for example, the variables inside the loop need to be viewed in the loop).
3. How to debug an error line?
- When the program throws an exception, PyCharm will automatically jump to the error line and display the stack information.
Summary: The core idea of debugging
- Locate the problem area: Reduce scope through error prompts or logs.
- Set breakpoints: Pause before and after suspicious code.
- Line-by-line tracking: Observe whether the variable meets expectations.
- Verification Fix: Repeat debugging after modification until correct.
The above is personal experience. I hope you can give you a reference and I hope you can support me more.