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plistlib Module

The plistlib module reads and writes property list (.plist) files, commonly used on macOS for storing application data and configuration.

Complexity Reference

Operation	Time	Space	Notes
loads()	O(n)	O(n)	n = data size; XML parsing overhead
dumps()	O(n)	O(n)	n = object size; XML generation
load()	O(n)	O(n)	n = file size
dump()	O(n)	O(n)	n = object size

Basic Parsing

Load from Bytes

import plistlib

# Parse plist data - O(n)
plist_bytes = b"""<?xml version="1.0"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
 "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>Name</key>
  <string>John Doe</string>
  <key>Age</key>
  <integer>30</integer>
</dict>
</plist>"""

data = plistlib.loads(plist_bytes)  # accepts bytes/bytearray
print(data['Name'])  # "John Doe"
print(data['Age'])   # 30

Load from File

import plistlib

# Read plist from file - O(n)
with open("settings.plist", "rb") as f:
    data = plistlib.load(f)

print(data['version'])
print(data['settings'])

Data Types

Supported Types

plistlib only supports a limited set of types. Dictionary keys must be strings, and values must be one of: str, int, float, bool, bytes, datetime.datetime, dict, list, or tuple. Unsupported types raise TypeError.

import datetime
import plistlib

# Create plist-compatible data
data = {
    'name': 'MyApp',
    'version': '1.0',
    'count': 42,
    'ratio': 3.14,
    'enabled': True,
    'items': ['a', 'b', 'c'],
    'nested': {
        'key': 'value'
    },
    'binary': b'bytes',
    'date': datetime.datetime.now()
}

# Convert to plist bytes - O(n)
plist_bytes = plistlib.dumps(data, sort_keys=True)
print(plist_bytes.decode('utf-8')[:200])  # Show first 200 chars

Writing Plist Files

Save Configuration

import plistlib

# Application settings
settings = {
    'version': '1.0',
    'theme': 'dark',
    'window_size': [1024, 768],
    'last_opened': '/Users/john/documents',
    'plugins_enabled': ['plugin1', 'plugin2'],
    'preferences': {
        'auto_save': True,
        'auto_save_interval': 300
    }
}

# Write to file - O(n)
with open("app_settings.plist", "wb") as f:
    plistlib.dump(settings, f)

Binary Vs XML Format

import plistlib

data = {'name': 'test', 'value': 123}

# XML format (text, human-readable) - O(n)
xml_bytes = plistlib.dumps(data, sort_keys=True, fmt=plistlib.FMT_XML)

# Binary format (compact, often smaller) - O(n)
binary_bytes = plistlib.dumps(data, sort_keys=True, fmt=plistlib.FMT_BINARY)

print(f"XML size: {len(xml_bytes)} bytes")
print(f"Binary size: {len(binary_bytes)} bytes")

macOS Application Data

Preferences Handling

import plistlib
from pathlib import Path

def get_app_preferences(app_name):
    """
    Load macOS application preferences.

    Time: O(n) where n = file size
    Space: O(n)
    """
    # Typical macOS preferences location
    pref_file = Path.home() / f".{app_name}_prefs.plist"

    if pref_file.exists():
        with open(pref_file, "rb") as f:
            return plistlib.load(f)

    return {}

def save_app_preferences(app_name, prefs):
    """
    Save macOS application preferences.

    Time: O(n) where n = data size
    Space: O(n)
    """
    pref_file = Path.home() / f".{app_name}_prefs.plist"

    with open(pref_file, "wb") as f:
        plistlib.dump(prefs, f)

# Usage
prefs = get_app_preferences('myapp')
prefs['last_window_pos'] = [100, 200, 800, 600]
save_app_preferences('myapp', prefs)

Info.plist Parsing

import plistlib
from pathlib import Path

def read_app_info(bundle_path):
    """
    Read macOS app bundle Info.plist.

    Time: O(n) where n = file size
    Space: O(n)
    """
    info_plist = Path(bundle_path) / "Contents" / "Info.plist"

    if info_plist.exists():
        with open(info_plist, "rb") as f:
            return plistlib.load(f)

    raise FileNotFoundError(f"No Info.plist in {bundle_path}")

# Usage
app_bundle = "/Applications/MyApp.app"
info = read_app_info(app_bundle)
print(f"App name: {info.get('CFBundleName')}")
print(f"Version: {info.get('CFBundleVersion')}")
print(f"Executable: {info.get('CFBundleExecutable')}")

Data Conversion

From Dictionary to Plist

import plistlib
from datetime import datetime

# Create structured data
manifest = {
    'title': 'Project Files',
    'version': 1,
    'created': datetime.now(),
    'files': [
        {
            'name': 'main.py',
            'size': 2048,
            'modified': datetime.now()
        },
        {
            'name': 'config.yaml',
            'size': 512,
            'modified': datetime.now()
        }
    ]
}

# Serialize - O(n)
plist_data = plistlib.dumps(manifest, sort_keys=True, fmt=plistlib.FMT_XML)

# Write to file
with open("manifest.plist", "wb") as f:
    f.write(plist_data)

Round-trip Operations

import plistlib

# Original data
original = {
    'strings': ['a', 'b', 'c'],
    'numbers': [1, 2, 3],
    'nested': {'key': 'value'}
}

# Serialize - O(n)
plist_bytes = plistlib.dumps(original, fmt=plistlib.FMT_XML)

# Deserialize - O(n)
restored = plistlib.loads(plist_bytes)

# Verify round-trip
assert original == restored
print("✓ Round-trip successful")

Advanced Patterns

Configuration Manager

import plistlib
from pathlib import Path
from typing import Any, Dict

class PlistConfig:
    """Configuration manager using plist format."""

    def __init__(self, config_file: str):
        self.config_file = Path(config_file)
        self.data = {}
        self.load()

    def load(self):
        """Load config from file - O(n)"""
        if self.config_file.exists():
            with open(self.config_file, "rb") as f:
                self.data = plistlib.load(f)

    def save(self):
        """Save config to file - O(n)"""
        with open(self.config_file, "wb") as f:
            plistlib.dump(self.data, f, sort_keys=True)

    def get(self, key: str, default: Any = None) -> Any:
        """Get config value - O(1)"""
        return self.data.get(key, default)

    def set(self, key: str, value: Any):
        """Set config value - O(1)"""
        self.data[key] = value

    def update(self, **kwargs):
        """Update multiple values - O(k) where k = keys"""
        self.data.update(kwargs)

# Usage
config = PlistConfig("app.plist")
config.set('debug', True)
config.set('port', 8000)
config.save()

Formats Available

import plistlib

# XML format (default)
# FMT_XML = 'xml'
# - Human readable
# - Larger file size
# - Text format

# Binary format (compact)
# FMT_BINARY = 'binary'
# - Not human readable
# - Smaller file size
# - Binary format

# Use FMT_XML for config files (human readable)
# Use FMT_BINARY for data files (compact)

Related Modules

• json Module - JSON format alternative
• pickle Module - Python object serialization
• configparser Module - INI configuration files
• pathlib Module - File path handling