selv 1.0.0

A Python decorator for logging attribute changes in classes

Selv

A Python decorator for logging attribute changes in class. Track every modification to your object's attributes with automatic logging and changelog.

Motivation

Tracking attribute changes helps me understand how a complex class behaves and speeds up debugging when issues occur. Having said this, I need a simple way to log all attribute changes without writing boilerplate code for each attribute.

Features

• Automatic attribute change tracking: Decorated class automatically log all attribute changes
• Container support: Tracks changes to dictionaries, lists, sets, and tuples, including nested modifications
• Flexible logging: Use good ol print statement or any custom logger function
• View changelog: Query complete change history for any attribute

Installation

pip install selv

Or using mighty uv:

uv add selv

Usage

Tracking changes

from selv import selv

@selv
class Counter:
    def __init__(self):
        self.value = 0

    def increment(self):
        self.value += 1

    def decrement(self):
        self.value -= 1

# Create counter and use it
counter = Counter()
counter.increment()
counter.decrement()

# Changes are automatically logged:
# [Counter] value: 0 -> 1
# [Counter] value: 1 -> 0

View changelog

# View all changes
all_changes = counter.view_changelog()
print(all_changes)
# [
#   {'time': datetime, 'attr': 'value', 'from': None, 'to': 0},
#   {'time': datetime, 'attr': 'value', 'from': 0, 'to': 1},
#   {'time': datetime, 'attr': 'value', 'from': 1, 'to': 0}
# ]

# View changes for specific attribute
value_changes = counter.view_changelog("value")
print(value_changes)
# [
#   {'time': datetime, 'from': None, 'to': 0},
#   {'time': datetime, 'from': 0, 'to': 1},
#   {'time': datetime, 'from': 1, 'to': 0}
# ]

# View changes grouped by attribute
grouped = counter.view_changelog(format="attr")
# {
#   'value': [
#     {'time': datetime, 'from': None, 'to': 0},
#     {'time': datetime, 'from': 0, 'to': 1},
#     {'time': datetime, 'from': 1, 'to': 0}
#   ]
# }

Parameters

The @selv decorator has a few parameters to customize its behavior.

1. track_private (bool, default: True)

   • When True: Tracks all attributes including those starting with _ (private attributes)
   • When False: Only tracks public attributes (those not starting with _)

2. logger (Callable[[str], None], default: print)

   • Function to use for logging change messages (e.g., logging.info, logging.debug)
   • Can be any function that accepts a string argument

License

MIT License - see LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.