Comment

Ilya Rusin

copy.deepcopy is way slower than dict comprehension -
https://stackoverflow.com/questions/20772885/is-python-deepcopy-more-efficient-than-custom-code-or-less-efficient-predictabl

"The reasons why deepcopy is so much slower than the dict comprehension + list copy are:

 - deepcopy is multi-purpose function - it works for mostly any kind of object
 - deepcopy is implemented in python whilst dict comprehension and list slicing is done at lower level

And most imporantly:

 - deepcopy makes copies of the elements inside containers recursively, whilst your dict comprehension does not."