zljubi...@gmail.com writes: > Hi, > > consider this example: > > from typing import Dict, List > > > class chk_params: > def execute(self, params: Dict[str, List] = None): > if params is None: > params = {} > > for k, v in params.items(): > params[k] = [val + 10 for val in v] > > return params.values() > > params = { > 'A' : [1], > 'B': [2], > 'C': [3], > 'D': [4], > 'E': [5] > } > print(params) > params_obj = chk_params() > > print(params_obj.execute(params = params)) > print(params) > > Output is: > {'A': [1], 'B': [2], 'C': [3], 'D': [4], 'E': [5]} > dict_values([[11], [12], [13], [14], [15]]) > {'A': [11], 'B': [12], 'C': [13], 'D': [14], 'E': [15]} > > I expected that last print statement will show original parameters A=1, > B=2... but this is not the case. > > How to construct the method parameters, with params parameter as type of > Dict[str, List], but at the same time keep params as local dictionary to the > chk_params.execute() method?
The execute method modifies the dict being passed into it. If you don't want that behaviour, you can pass in a copy of your params object. dict(params) will make a shallow copy, which will work in this particular case. If the execute method were to do in-place modification operation on the values (perhaps using v.append or v.extend in its loop), you'd need a deep copy provided by the standard library's copy.deepcopy function. -- regards, kushal -- https://mail.python.org/mailman/listinfo/python-list