Basic Debugging Tools

Debugging is an essential skill in programming, helping you identify and resolve errors in your code efficiently. Python provides several built-in tools and practices for debugging.

1. Debugging with Print Statements

Using print() statements is one of the simplest ways to debug your code by displaying values of variables or execution flow.

Example:

# Example of debugging with print
number = 10
def increment(num):
    print(f"Input number: {num}")  # Debugging statement
    return num + 1

result = increment(number)
print(f"Result: {result}")

2. The pdb Debugger

Python includes a built-in debugger module, pdb, for step-by-step execution and inspection of code.

Key Commands:

• l (list): Display code around the current line.
• n (next): Execute the next line.
• s (step): Step into a function.
• c (continue): Continue execution until the next breakpoint.

Example:

import pdb

def divide(a, b):
    pdb.set_trace()  # Start debugging session
    return a / b

result = divide(10, 2)
print(result)

3. Debugging in VSCode

VSCode provides an integrated debugging environment with powerful features.

Steps:

1. Set Breakpoints: Click next to the line numbers to set breakpoints.
2. Start Debugging: Press F5 or go to the Debug panel and select "Start Debugging."
3. Inspect Variables: Use the "Variables" section to monitor values.
4. Step Over/Into/Out: Use the controls to step through the code.

4. Using Logging for Debugging

The logging module provides a more structured approach to debugging compared to print().

Levels:

• DEBUG: Detailed information for diagnostics.
• INFO: General events.
• WARNING: Something unexpected happened but not critical.
• ERROR: More serious issues.
• CRITICAL: Severe errors.

Example:

import logging

logging.basicConfig(level=logging.DEBUG)

def add(a, b):
    logging.debug(f"Adding {a} and {b}")
    return a + b

result = add(5, 7)
logging.info(f"Result: {result}")

5. Catching Exceptions for Debugging

Using try-except blocks can help debug runtime errors by catching exceptions and displaying relevant information.

Example:

try:
    result = 10 / 0
except ZeroDivisionError as e:
    print(f"Error: {e}")

numbers = [1, 2, 3, 4]
def multiply_by_two(nums):
    for i in range(len(nums)):
        nums[i] *= 2
    return numbs  # Typo in variable name

result = multiply_by_two(numbers)
print(result)

By mastering these debugging techniques, you can effectively identify and resolve issues in your Python programs!