All 15 Magic Methods & Operator Overloading questions
More in Magic Methods & Operator Overloading
How do __len__, __getitem__, and __setitem__ let a custom class act like a sequence or mapping? How does __call__ let an instance of a class be invoked like a function? How do comparison magic methods like __lt__, __le__, __gt__, and __ge__ support custom sorting? How does __contains__ let you customize the behavior of the 'in' operator? How do context manager magic methods __enter__ and __exit__ work, and what does __exit__'s return value control? What is the difference between __new__ and __init__, and when would you override __new__? How do __iadd__ and other in-place operator methods (__isub__, __imul__) differ from their non-in-place counterparts? How does __bool__ (or the legacy __nonzero__) determine an object's truthiness, and what's the fallback if it's not defined? How does __slots__ interact with magic methods and instance attribute storage?
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How do you implement custom attribute access with __getattr__ versus __getattribute__?

Intermediate

Answer

__getattr__(self, name) is only called as a fallback when normal attribute lookup fails (attribute not found through __dict__ or the class hierarchy) -- ideal for lazy attributes or proxies. __getattribute__(self, name) is called for every attribute access unconditionally, making it more powerful but riskier (easy to cause infinite recursion) since you must carefully delegate to super().__getattribute__() for normal attributes.
class LazyConfig:
    def __getattr__(self, name):
        print(f'Loading {name} on demand')
        value = load_from_disk(name)
        setattr(self, name, value)  # cache it
        return value

config = LazyConfig()
print(config.database_url)  # triggers lazy load only once
Real-world example A configuration object lazily fetches and caches settings from a remote service only when first accessed, using __getattr__ to avoid an expensive upfront load of every possible setting.

Common follow-ups: Why is __getattribute__ more dangerous to override than __getattr__?;How does this relate to descriptors?

Descriptors & Properties;Metaclasses & Class Customization
All 15 Magic Methods & Operator Overloading questions