Python can make a dictionary immutable without copying data!

Usually, to protect configurations and the overall state, a copy of the dictionary is made, which creates unnecessary memory allocations.

safe = dict(config)

MappingProxyType creates a read-only proxy over a dictionary — writing through it becomes impossible, but the data is not copied.

readonly["debug"] = True  # TypeError

At the same time, the proxy remains alive: if the original dictionary changes, the changes will automatically be reflected in the read-only view.

config["debug"] = True

This is especially useful for configurations, internal APIs, overall state, and data protection within libraries.

def get_settings():
    return MappingProxyType(settings)

🔥 MappingProxyType allows you to provide a read-only view of the dictionary without copying and without the risk of mutation through the returned object.

#Python #Immutable #DataProtection #MappingProxyType #ProgrammingTips #NoCopy

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