Python Debugging with print() vs the Debugger

This guide explains debugging with print() vs the debugger through a focused Python example. You will learn the behavior to expect, why it matters in a real program, and how to recognize the common mistakes before applying it in your own project.

What You Will Learn

Print debugging exposes values at selected points; a debugger pauses execution, inspects variables and steps between statements. Both help when outcomes differ from expectations.

When and Why to Use It

The following example focuses on a practical use of Debugging with print() vs the Debugger.

Step-by-Step Example

def apply_discount(price, rate):
    discounted_price = price * (1 - rate)
    print("DEBUG discounted_price:", discounted_price)
    return discounted_price

print(apply_discount(80, 0.25))

Understanding the Example

The debug line shows the intermediate discounted price before the function returns the same value. In PyCharm, a breakpoint can inspect it without modifying source output.

Expected Output

DEBUG discounted_price: 60.0
60.0

Important Behavior and Edge Cases

Temporary prints can leak private information and clutter production output. Use a debugger or configured logging for larger applications.

Try It Yourself

Place a breakpoint on the multiplication line and inspect price, rate and discounted_price.

Common Beginner Mistakes

• Temporary prints can leak private information and clutter production output. Use a debugger or configured logging for larger applications.
• Handling the symptom rather than identifying the failing operation, or letting a broad exception handler hide defects.
• Skipping the practice step and assuming the example covers every input. Test at least one normal case and one edge case relevant to this topic.

Key Takeaways

• Print debugging exposes values at selected points; a debugger pauses execution, inspects variables and steps between statements.
• The debug line shows the intermediate discounted price before the function returns the same value.
• Apply the technique deliberately, checking its documented input requirements and failure behavior before integrating it into a larger project.