python - Execution order of nested dictionary comprehension

Question

This question already has answers here: question from:https://stackoverflow.com/questions/65935560/execution-order-of-nested-dictionary-comprehension

Answer 1

You need to switch your iteration logic. Default order of iteration inside dictionary (or list) comprehension goes from left to right:

>>> data = [{'A': 123}, {'B': 456}, {'C': 789}]

>>> {k: v for d in data for k, v in d.items()}
{'A': 123, 'B': 456, 'C': 789}

You can create nested dictionary comprehension, list comprehension or generator expression using {}, [] and () respectively which are the exceptions for the left to right execution order I mentioned earlier. All these operations create new objects, and they execute inside their own scope.