How to modify Python DataClass inside map(lambda: )

Question

I want to modify a dataclass(dataclass_json) in a map/lambda. With dictionaries you can perform a dict.update({"key": "value"}) within a lambda, but how does one update a dataclass's value without:

MyDataClass.name = "class name" # this works outside a lambda

(Example below is the incorrect syntax I know)

repositories_list: List[MyDataClass]
_ = list(map(lambda repository: repository.name = my_func(repository), repositories_list))

Of course I can't just use =, so how's this done?

Answer 1

You can access setattr , the function that does the actual work during an attribute assignment, directly:

list(map(lambda r: setattr(r, "name", my_func(repository)), repositories_list))

This pattern is not dataclass-specific, it works with any python object.

Answer 2

Solved it with replace from dataclasses

from dataclasses import replace
repositories_list = list(map(lambda repository: replace(repository, name=my_func(repository)), repositories_list))