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PyPowSyBl uses Python’s standard logging framework to provide detailed information about operations, errors, and debugging information.

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Overview

All PyPowSyBl logs are sent to the 'powsybl' logger. By default, this logger has a null handler, so no logs are printed unless you configure logging.

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Basic Logging Setup

Enable logging to see PyPowSyBl output: 
import logging

# Create basic logging configuration
logging.basicConfig()

# Set log level for PyPowSyBl
logging.getLogger('powsybl').setLevel(logging.INFO)

import pypowsybl as pp
# Now you'll see INFO level messages

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Log Levels

PyPowSyBl supports standard Python logging levels:
Most detailed logging. Shows:
  • Memory configuration
  • Detailed operation steps
  • Internal state changes
logging.getLogger('powsybl').setLevel(logging.DEBUG)
Use for: Development and troubleshooting
General informational messages:
  • Operation start/completion
  • Major steps in calculations
  • Configuration values
logging.getLogger('powsybl').setLevel(logging.INFO)
Use for: Normal operation monitoring
Warnings about potential issues:
  • Deprecated features
  • Unusual conditions
  • Non-critical problems
logging.getLogger('powsybl').setLevel(logging.WARNING)
Use for: Production (default recommendation)
Error messages:
  • Operation failures
  • Invalid configurations
  • Critical issues
logging.getLogger('powsybl').setLevel(logging.ERROR)
Use for: Minimal logging

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Java TRACE Logging

For extremely detailed Java-side logging (logback TRACE level), use level 1: 
import logging

logging.basicConfig()
logging.getLogger('powsybl').setLevel(1)

import pypowsybl as pp
# Shows detailed Java-side execution
TRACE logging (level 1) produces very verbose output. Use only for deep debugging.

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Custom Log Format

Create more readable log output: 
import logging

# Configure format with timestamp
logging.basicConfig(
    format='%(asctime)s - %(levelname)s - %(message)s',
    level=logging.INFO
)

logging.getLogger('powsybl').setLevel(logging.INFO)

import pypowsybl as pp
# Output: 2026-03-06 10:30:45,123 - INFO - Max heap is 4096 MB

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Format Options

# Detailed format
logging.basicConfig(
    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
    datefmt='%Y-%m-%d %H:%M:%S'
)

# Simple format
logging.basicConfig(
    format='[%(levelname)s] %(message)s'
)

# With module information
logging.basicConfig(
    format='%(asctime)s - %(name)s - %(module)s - %(levelname)s - %(message)s'
)

​
Logging to File

Save logs to a file instead of console: 
import logging

logging.basicConfig(
    filename='pypowsybl.log',
    filemode='w',  # 'w' to overwrite, 'a' to append
    format='%(asctime)s - %(levelname)s - %(message)s',
    level=logging.INFO
)

logging.getLogger('powsybl').setLevel(logging.DEBUG)

import pypowsybl as pp
# Logs written to pypowsybl.log

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Multiple Handlers

Log to both console and file: 
import logging
import sys

# Create logger
logger = logging.getLogger('powsybl')
logger.setLevel(logging.DEBUG)

# Console handler (INFO level)
console_handler = logging.StreamHandler(sys.stdout)
console_handler.setLevel(logging.INFO)
console_format = logging.Formatter('[%(levelname)s] %(message)s')
console_handler.setFormatter(console_format)

# File handler (DEBUG level)
file_handler = logging.FileHandler('pypowsybl_debug.log')
file_handler.setLevel(logging.DEBUG)
file_format = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
file_handler.setFormatter(file_format)

# Add handlers
logger.addHandler(console_handler)
logger.addHandler(file_handler)

import pypowsybl as pp
# INFO+ to console, DEBUG+ to file

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Environment-Specific Configuration

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Development

import logging

logging.basicConfig(
    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
    level=logging.DEBUG
)

logging.getLogger('powsybl').setLevel(logging.DEBUG)

​
Production

import logging

logging.basicConfig(
    filename='/var/log/pypowsybl/app.log',
    format='%(asctime)s - %(levelname)s - %(message)s',
    level=logging.WARNING
)

logging.getLogger('powsybl').setLevel(logging.WARNING)

​
Testing

import logging

logging.basicConfig(
    format='[%(levelname)s] %(message)s',
    level=logging.ERROR
)

logging.getLogger('powsybl').setLevel(logging.ERROR)
# Suppress most output during tests

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Jupyter Notebook Configuration

For Jupyter notebooks: 
import logging
import sys

# Configure logging for notebook
logging.basicConfig(
    stream=sys.stdout,
    format='%(asctime)s - %(levelname)s - %(message)s',
    level=logging.INFO
)

logging.getLogger('powsybl').setLevel(logging.INFO)

import pypowsybl as pp

​
Filtering Specific Loggers

Control logging for specific modules: 
import logging

logging.basicConfig(level=logging.INFO)

# General pypowsybl logs at INFO
logging.getLogger('powsybl').setLevel(logging.INFO)

# Loadflow logs at DEBUG
logging.getLogger('powsybl.loadflow').setLevel(logging.DEBUG)

# Security analysis logs at WARNING only
logging.getLogger('powsybl.security').setLevel(logging.WARNING)

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Temporary Log Level Changes

Change log level temporarily: 
import logging

logger = logging.getLogger('powsybl')
original_level = logger.level

try:
    # Temporarily enable debug
    logger.setLevel(logging.DEBUG)
    # ... operations that need detailed logging ...
    network = pp.network.load('problematic_network.xiidm')
finally:
    # Restore original level
    logger.setLevel(original_level)

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Complete Configuration Example

import logging
import logging.handlers
import sys
from pathlib import Path

# Create logs directory
log_dir = Path('logs')
log_dir.mkdir(exist_ok=True)

# Create logger
logger = logging.getLogger('powsybl')
logger.setLevel(logging.DEBUG)

# Console handler - INFO and above
console = logging.StreamHandler(sys.stdout)
console.setLevel(logging.INFO)
console_format = logging.Formatter(
    '[%(levelname)-8s] %(message)s'
)
console.setFormatter(console_format)

# File handler - DEBUG and above, rotates at 10MB
file_handler = logging.handlers.RotatingFileHandler(
    log_dir / 'pypowsybl.log',
    maxBytes=10*1024*1024,  # 10 MB
    backupCount=5
)
file_handler.setLevel(logging.DEBUG)
file_format = logging.Formatter(
    '%(asctime)s - %(name)s - %(levelname)s - %(message)s',
    datefmt='%Y-%m-%d %H:%M:%S'
)
file_handler.setFormatter(file_format)

# Error file handler - ERROR and above only
error_handler = logging.FileHandler(log_dir / 'errors.log')
error_handler.setLevel(logging.ERROR)
error_handler.setFormatter(file_format)

# Add all handlers
logger.addHandler(console)
logger.addHandler(file_handler)
logger.addHandler(error_handler)

import pypowsybl as pp
logger.info("PyPowSyBl logging configured")

​
Common Logging Scenarios

import logging

logging.basicConfig(
    format='%(asctime)s - %(levelname)s - %(message)s'
)
logging.getLogger('powsybl').setLevel(logging.DEBUG)

import pypowsybl as pp

# Debug output will show import details
network = pp.network.load('problematic_file.xiidm')

import logging

logging.basicConfig(
    format='%(asctime)s - %(message)s',
    level=logging.INFO
)
logging.getLogger('powsybl').setLevel(logging.INFO)

import pypowsybl as pp

# Will show progress of calculation
result = pp.security.run_ac(large_network)

import logging
import logging.handlers

logger = logging.getLogger('powsybl')
logger.setLevel(logging.WARNING)

handler = logging.handlers.RotatingFileHandler(
    '/var/log/pypowsybl/errors.log',
    maxBytes=50*1024*1024,
    backupCount=10
)
handler.setFormatter(
    logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
)
logger.addHandler(handler)

import pypowsybl as pp
# Only warnings and errors logged

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Verifying Configuration

Check your logging setup: 
import logging

logger = logging.getLogger('powsybl')

print(f"Logger level: {logging.getLevelName(logger.level)}")
print(f"Effective level: {logging.getLevelName(logger.getEffectiveLevel())}")
print(f"Handlers: {logger.handlers}")
print(f"Propagate: {logger.propagate}")

# Test log output
logger.debug("Debug message")
logger.info("Info message")
logger.warning("Warning message")
logger.error("Error message")

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Troubleshooting

Check:
  1. Logging configured before importing pypowsybl
  2. Log level set appropriately
  3. Handler added to logger
import logging
logging.basicConfig()  # This must come first
logging.getLogger('powsybl').setLevel(logging.INFO)
import pypowsybl as pp  # Then import
Increase log level:
logging.getLogger('powsybl').setLevel(logging.WARNING)
Or filter specific modules:
logging.getLogger('powsybl.network').setLevel(logging.ERROR)
Lower the log level:
logging.getLogger('powsybl').setLevel(logging.DEBUG)
For Java trace logs:
logging.getLogger('powsybl').setLevel(1)

​
Best Practices

1

Configure early

Set up logging before importing pypowsybl:
import logging
logging.basicConfig()
logging.getLogger('powsybl').setLevel(logging.INFO)
import pypowsybl as pp
2

Use appropriate levels

  • Development: DEBUG
  • Production: WARNING
  • Testing: ERROR
3

Add context to format

Include timestamps and module names:
logging.basicConfig(
    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)
4

Rotate log files

Use RotatingFileHandler for long-running applications.

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Next Steps

Network

Start working with networks

Load Flow

Run your first load flow

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