Debugging PyneCore Scripts

This guide covers debugging techniques for PyneCore scripts, including inspection of Series variables and execution flow.

Overview

PyneCore provides several debugging approaches to help you understand and troubleshoot your Pine Script translations:

  • Print statements: Traditional Python debugging
  • Pine Script logging: Native Pine Script debug functions
  • IDE debugging: Step-through debugging with considerations for AST transformations

The simplest debugging approach is using Python’s built-in print function:

  # Basic print debugging
print("Current bar_index:", bar_index)
print("Close price:", close)
print("Variable value:", my_variable)

PyneCore supports Pine Script’s native logging functions, which provide colorized output and better formatting:

log.info()

Use for general information and variable inspection:

  log.info("Current bar index: {0}", bar_index)
log.info("Close price: {0}", close)
log.info("SMA value: {0}", ta.sma(close, 20))

log.warning()

Use for warnings and potential issues:

  if volume == 0:
    log.warning("Zero volume detected at bar {0}", bar_index)

log.error()

Use for error conditions:

  if close < 0:
    log.error("Invalid close price: {0}", close)

Formatting

Pine Script logging supports formatting with curly braces:

  log.info("Bar {0}: Open={1}, High={2}, Low={3}, Close={4}",
         bar_index, open, high, low, close)

Limiting Debug Output

To avoid overwhelming output, use bar_index to limit debug messages:

  # Only log first 10 bars
if bar_index < 10:
    log.info("Bar {0}: Close={1}", bar_index, close)

# Log every 100 bars
if bar_index % 100 == 0:
    log.info("Processing bar {0}", bar_index)

# Log specific conditions
if ta.crossover(close, ta.sma(close, 20)):
    log.info("Golden cross at bar {0}", bar_index)

IDE Debugging

You can use your IDE’s debugger with PyneCore scripts, but be aware of AST transformations:

AST Transformations

Before execution, PyneCore applies AST transformations (see AST Transformations for details). This affects debugging:

  • Series variables: May be stored in globals() dictionary
  • Persistent variables: Renamed with special prefixes
  • Function isolation: Functions may have additional parameters

Debugging with Transformations

When using the debugger:

  1. Series variables: Look for them in globals() if not found in local scope
  2. Persistent variables: Check for renamed versions with __persistent_ prefix
  3. Function parameters: May include additional isolation parameters

Best Practices

  1. Use Pine Script logging: Prefer log.info(), log.warning(), and log.error() over print()
  2. Limit output: Always use bar_index checks to prevent excessive logging
  3. Structured logging: Use consistent formatting for easier analysis
  4. Remove debug code: Clean up debug statements before production
  5. Test incrementally: Add debug statements progressively to isolate issues