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> 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 mappi

• 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/