Use Run Code / Run when you want to execute your program and see its output. Use Debug when you want to pause at a line, inspect variables, and work out why a result is wrong. Debugging is especially useful when your code runs without an error but produces an unexpected answer.
This guide uses the CodeUtility Python executor and a small calculation example. The breakpoint-and-step workflow also applies to other executors where Debug is available. Runtime support and controls can vary; use a supported server runtime for this Python walkthrough. Screenshots show the English interface.
1. Try a small program with a logic bug
Open the Python executor, choose Python 3.11 in the version menu, and enter the following four lines. A price of 12 multiplied by a quantity of 3 should give 36. This program deliberately uses addition, so it produces 15.
price = 12
quantity = 3
total = price + quantity
print(total)2. Set a breakpoint before starting Debug
Click in the left gutter beside line 3, the line containing total = price + quantity. A red breakpoint marker appears. A breakpoint tells the debugger where to pause. Click the marker again to remove it. Place breakpoints on executable statements rather than blank lines or comments.
3. Start Debug and inspect the values
Select Debug in the editor toolbar; hover over an icon to see its label. Wait for the debugger window to report Paused at line 3. Paused means the program is waiting for your next debugging action.
Look under VARIABLES: price is 12 and quantity is 3. Line 3 has not executed yet, so total is not listed. The highlighted line is the next statement to execute. The CALL STACK shows where execution is currently paused.
4. Step through the calculation
Click Step Over once. Execution moves to line 4, and total now appears with the value 15. This shows that the wrong answer comes from adding the two values on line 3.
Continue resumes until another breakpoint is reached or the program finishes. Step Over executes the current statement without stepping into a called function. Step Into enters a called function when supported. Step Out runs until the current function returns. Stop, shown as a square icon, ends the debugging session.
5. Fix the code and run it again
Select Continue to finish the example, or Stop to end the session. Replace the plus sign on line 3 with a multiplication sign, then select Run Code / Run to check the output. You should see 36. You can also start Debug again and use Step Over to verify the corrected value.
price = 12
quantity = 3
total = price * quantity
print(total)If debugging does not pause where you expect
Check that a red breakpoint is set before starting Debug, that you selected Debug, and that the program actually reaches that line. Choose an executable line and confirm that the selected runtime supports debugging. Syntax errors can prevent execution from reaching a breakpoint. If your program requests input, provide it in the terminal so execution can continue.
For your next debugging session, place a breakpoint just before the suspicious calculation, inspect its inputs, and step forward until you find the first unexpected value. If you only need the final output, select Run Code.