Python `str` vs. `repr`: What's the Difference in Object Representation?

str and __repr__: Unlocking the Difference in Python Representations

The distinction between str and repr in Python lies in their fundamental objectives:

repr for Unambiguous Identity

__repr__, as its name suggests, aims to provide an unambiguous "representation" of an object. Its focus is on providing enough information to recreate the exact same object later. The default implementation returns the class name and attributes, separating them by parameters delimiters. This format ensures that the result can be evaluated with eval(), allowing for the reconstitution of the object.

str for Human Readability

__str__, on the other hand, prioritizes human readability over precision. It's meant to generate a string that can be easily understood by a human. It often omits unnecessary details and may format the output to be more visually appealing.

Key Differences

• repr strives for unambiguous representation, while str aims for readability.
• str is meant for user-facing output, while repr is more suited for debugging or object introspection.
• Default implementation of repr is typically useless but can be used for debugging when str is not defined.
• Containers (e.g., lists, dictionaries) use the repr of their contained objects for __str__.

Best Practices

• Always define repr for your custom classes to ensure proper object identification.
• Only implement str if you want a human-readable string representation that might differ from the __repr__.
• Use %r (repr() formatting) in repr to ensure unambiguous evaluation.
• Use %s (str() formatting) in str to format the string for readability.

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