Debug Your Application (Python)

Python Application Debugging Overview

Debugging Python applications in MatrixOS primarily involves using print statements. Since Python applications run in the PikaPython interpreter, the print function is your main tool for understanding program flow and variable states.

Print Debugging

The print function is the primary debugging tool for Python applications in MatrixOS. Use print statements strategically to understand program flow and variable states.

Basic Print Usage

def my_function():
    print("Starting function")

    # Your code here
    result = some_calculation()
    print(f"Calculation result: {result}")

    return result

# Debug variable values
value = 42
print(f"Debug: value = {value}")

Tracking Program Flow

def complex_operation():
    print("Step 1: Initializing")
    # initialization code

    print("Step 2: Processing data")
    # processing code

    print("Step 3: Finalizing")
    # finalization code

    print("Operation complete")

Debugging Variables

# Print variable types and values
my_variable = 123
print(f"Variable type: {type(my_variable)}, value: {my_variable}")

# Print multiple values
x, y = 5, 10
print(f"Coordinates: x={x}, y={y}")

# Print list/array contents
my_list = [1, 2, 3, 4, 5]
print(f"List contents: {my_list}")

Debugging Loops

# Track loop iterations
for i in range(5):
    print(f"Loop iteration: {i}")
    # Your loop code here

# Debug while loops
counter = 0
while counter < 3:
    print(f"While loop: counter = {counter}")
    counter += 1

Debugging Functions

def calculate(a, b):
    print(f"Function called with a={a}, b={b}")
    result = a + b
    print(f"Returning result: {result}")
    return result

# Call the function
answer = calculate(3, 4)
print(f"Final answer: {answer}")

Debugging MatrixOS API Calls

# Debug LED operations
print("Setting LED color")
MatrixOS.LED.SetColor(Point(3, 3), Color(255, 0, 0), 255)
print("LED color set, updating display")
MatrixOS.LED.Update(255)
print("Display updated")

# Debug keypad events
key_event = MatrixOS.KeyPad.Get(1000)
if key_event is not None:
    print(f"Key pressed at position ({key_event.xy.x}, {key_event.xy.y})")
else:
    print("No key pressed")

# Debug timing
start_time = MatrixOS.SYS.Millis()
# Your code here
end_time = MatrixOS.SYS.Millis()
print(f"Operation took {end_time - start_time} milliseconds")

Debugging Conditional Logic

def check_value(value):
    print(f"Checking value: {value}")

    if value < 0:
        print("Value is negative")
    elif value == 0:
        print("Value is zero")
    else:
        print("Value is positive")

    return value

Formatted Output for Clarity

# Use separators for clarity
print("=" * 30)
print("Starting Debug Section")
print("=" * 30)

# Format numbers
value = 3.14159
print(f"Pi value: {value:.2f}")  # Two decimal places

# Align output
for i in range(3):
    print(f"Item {i:2d}: {'Active' if i > 0 else 'Inactive'}")

Best Practices for Print Debugging

1. Be Descriptive: Make print messages clear and informative

   # Good
   print(f"Processing key at position ({x}, {y})")
   
   # Less helpful
   print("here")

2. Include Context: Show what part of the code is executing

   print("MainLoop: Checking for key events")

3. Show Variable States: Include relevant variable values

   print(f"LED brightness set to {brightness}/255")

4. Use Consistent Formatting: Make output easy to read

   print(f"[INFO] System ready")
   print(f"[ERROR] Failed to initialize")
   print(f"[DEBUG] Variable x = {x}")

5. Track Entry and Exit: Show when functions start and end

   def my_function():
       print(">>> Entering my_function")
       # function code
       print("<<< Exiting my_function")

Example: Complete Debug Session

Here's a practical example showing effective print debugging:

def interactive_app():
    """Example application with comprehensive print debugging"""

    print("=" * 40)
    print("Application Starting")
    print("=" * 40)

    # Initialize
    print("Initializing LED display...")
    MatrixOS.LED.Fill(Color(0, 0, 0), 0)
    MatrixOS.LED.Update(0)
    print("LED display initialized")

    # Main loop
    print("Entering main loop")
    loop_count = 0

    while loop_count < 10:
        print(f"\n--- Loop iteration {loop_count} ---")

        # Check for input
        print("Checking for key press...")
        key_event = MatrixOS.KeyPad.Get(100)

        if key_event is not None:
            x = key_event.xy.x
            y = key_event.xy.y
            print(f"Key detected at ({x}, {y})")

            # Process the key
            if key_event.info.state == 1:
                print(f"  Key pressed - lighting LED")
                MatrixOS.LED.SetColor(Point(x, y), Color(255, 0, 0), 255)
                MatrixOS.LED.Update(255)
            elif key_event.info.state == 2:
                print(f"  Key released - turning off LED")
                MatrixOS.LED.SetColor(Point(x, y), Color(0, 0, 0), 0)
                MatrixOS.LED.Update(0)
        else:
            print("No key press detected")

        loop_count += 1
        print(f"Loop {loop_count} complete")

    print("\n" + "=" * 40)
    print("Application Ending")
    print("=" * 40)

# Run the app
interactive_app()

Tips for Effective Print Debugging

• Start Simple: Add prints one at a time to isolate issues
• Remove When Done: Clean up debug prints after fixing issues
• Use Meaningful Labels: Make it clear what each print represents
• Watch for Timing: Too many prints can affect program timing
• Check Output Frequency: Avoid flooding output in fast loops

Remember: Print debugging is simple but powerful. Well-placed print statements can quickly reveal what your program is doing and help identify where issues occur.