7 Practical ReprMixin Patterns Every Python Developer Should Know

7 Ways to Write a Smarter ReprMixin in Python

1. Minimalistic ReprMixin

Shows all attributes in a simple key=value format

class ReprMixin:

    def __repr__(self):

        return f"<{self.__class__.__name__} {vars(self)}>"

2. Pretty ReprMixin (comma-separated)

Cleaner and more human-readable

class PrettyReprMixin:

    def __repr__(self):

        attrs = ", ".join(f"{k}={v!r}" for k, v in vars(self).items())

        return f"{self.__class__.__name__}({attrs})"

3. Whitelist ReprMixin

Only show specific attributes (by defining __repr_fields__).

class WhitelistReprMixin:

    __repr_fields__ = []



    def __repr__(self):

        fields = getattr(self, "__repr_fields__", vars(self).keys())

        attrs = ", ".join(f"{k}={getattr(self, k)!r}" for k in fields if hasattr(self, k))

        return f"{self.__class__.__name__}({attrs})"

Usage:

class User(WhitelistReprMixin):

    __repr_fields__ = ["username", "email"]



    def __init__(self, username, email, password):

        self.username = username

        self.email = email

        self.password = password

print(User("Joe", "[email protected]", "Glinteco is an awesome team"))

# User(username='Joe', email='[email protected]')

4. Blacklist ReprMixin

Hide sensitive fields (like password)

class BlacklistReprMixin:

    __repr_exclude__ = []



    def __repr__(self):

        attrs = ", ".join(

            f"{k}={v!r}" for k, v in vars(self).items() if k not in self.__repr_exclude__

        )

        return f"{self.__class__.__name__}({attrs})"

Usage:

class Account(BlacklistReprMixin):

    __repr_exclude__ = ["password"]



    def __init__(self, username, password):

        self.username = username

        self.password = password





print(Account("bob", "supersecret"))

# Account(username='bob')

5. Deep ReprMixin

Recursively represents nested objects

class DeepReprMixin: def __repr__(self): def safe_repr(obj): if isinstance(obj, (list, tuple, set)): return f"[{', '.join(map(safe_repr, obj))}]" elif isinstance(obj, dict): return f"{{{', '.join(f'{k}: {safe_repr(v)}' for k, v in obj.items())}}}" elif hasattr(obj, "__repr__") and not isinstance(obj, str): return obj.__repr__() return repr(obj) attrs = ", ".join(f"{k}={safe_repr(v)}" for k, v in vars(self).items()) return f"{self.__class__.__name__}({attrs})"

6. Compact ReprMixin (with truncation)

Useful for big objects to prevents flooding logs

class CompactReprMixin:

    __repr_maxlen__ = 30



    def __repr__(self):

        parts = []

        for k, v in vars(self).items():

            text = repr(v)

            if len(text) > self.__repr_maxlen__:

                text = text[:self.__repr_maxlen__] + "..."

            parts.append(f"{k}={text}")

        return f"{self.__class__.__name__}({', '.join(parts)})"

7. Dataclass-style ReprMixin

Sorts attributes alphabetically (like dataclasses)

class SortedReprMixin:

    def __repr__(self):

        attrs = ", ".join(

            f"{k}={v!r}" for k, v in sorted(vars(self).items(), key=lambda x: x[0])

        )

        return f"{self.__class__.__name__}({attrs})"