How can i use the sort function if i want to sort ascending by a criterion and descending by another criterion?

Question

I am trying to implement the A* algorithm in Python as a learning exercise. I have a list of nodes, called open , that contains strings that represent the names of graph nodes. Example: open["node_a", "node_b", "node_c"] . I also have two defaultdict dictionaries, f_estim and g , that contain values like {"name_of_node" : integer_representing_a_certain_cost_associated_to_the_node} . I am required to sort the open list ascending by the value associated in f_estim , and if that value is equal for two nodes, descending according to the value in g . I am sorting ascending like so: open.sort(key=lambda node: f_estim[node]) . How can i also sort descending when reaching two equal values? I could not find the answer in the documentation of the sort function. Thank you!

Answer 1

你可以这样做：

open.sort(key=lambda node: (f_estim[node], -g[node]))