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> Don't use classes for information. Use regular data structures (dict, list, tuple, set) and use functions to manipulate them. One problem is many of these da

> Don't use classes for information. Use regular data structures (dict, list, tuple, set) and use functions to manipulate them. One problem is many of these datastructures are easy to mutate. When I need to ensure immutability to a dictionary, for instance - quite often - I can't avoid wrapping it in a class and setting up an interface to lock down mutation. If Python had a way to declare immutable datastructure, similarly to Clojure, it would make life a lot easier...

galoisscobi 5y ago
Frozen dataclass instances (https://docs.python.org/3/library/dataclasses.html#frozen-instances https://docs.python.org/3/library/dataclasses.html#frozen-in...) might be of help.
- rmbyrro 5y ago
  Wasn't aware of this feature in dataclasses, that can be helpful in a few cases, thanks for pointing out
ciupicri 5y ago
> class types.MappingProxyType(mapping) > Read-only proxy of a mapping. It provides a dynamic view on the mapping’s entries, which means that when the mapping changes, the view reflects these changes. https://docs.python.org/3/library/types.html#types.MappingProxyType https://docs.python.org/3/library/types.html#types.MappingPr...
- rmbyrro 5y ago
  This can be helpful in some cases, but it's precisely what I sometimes need to avoid, which is protecting a dictionary and having changes affecting only its own scope. If function A passes a dict to function B, I would like: 1) Function A to keep the dict intact while function B can manipulate its content; 2) Function A can change the dict after passing to B, and B still keep the original copy, unaware of A's later changes. One way of doing this is by deep copying dictionaries around, but it can easily become a big performance issue.
  - ciupicri 5y ago
    It sounds like what you really want is an efficient way of copying dictionaries, perhaps copy on write, something like the cowdict [1] project. [1]: https://pypi.org/project/cowdict/ https://pypi.org/project/cowdict/

galoisscobi 5y ago

Frozen dataclass instances (https://docs.python.org/3/library/dataclasses.html#frozen-instances https://docs.python.org/3/library/dataclasses.html#frozen-in...) might be of help.

rmbyrro 5y ago
Wasn't aware of this feature in dataclasses, that can be helpful in a few cases, thanks for pointing out

ciupicri 5y ago

> class types.MappingProxyType(mapping) > Read-only proxy of a mapping. It provides a dynamic view on the mapping’s entries, which means that when the mapping changes, the view reflects these changes. https://docs.python.org/3/library/types.html#types.MappingProxyType https://docs.python.org/3/library/types.html#types.MappingPr...

rmbyrro 5y ago
This can be helpful in some cases, but it's precisely what I sometimes need to avoid, which is protecting a dictionary and having changes affecting only its own scope. If function A passes a dict to function B, I would like: 1) Function A to keep the dict intact while function B can manipulate its content; 2) Function A can change the dict after passing to B, and B still keep the original copy, unaware of A's later changes. One way of doing this is by deep copying dictionaries around, but it can easily become a big performance issue.
- ciupicri 5y ago
  It sounds like what you really want is an efficient way of copying dictionaries, perhaps copy on write, something like the cowdict [1] project. [1]: https://pypi.org/project/cowdict/ https://pypi.org/project/cowdict/