cb8bbd9745
Update formatting in every_nth Update formatting in shuffle Update formatting in has_duplicates Update formatting in group_by Update formatting in sum_by Update formatting in zip Update formatting in longest_item Update formatting in bifurcate_by Update formatting in difference_by Update formatting in clamp_number Update formatting in min_by Update formatting in max_by Update formatting in union Update formatting in n_times_string Update formatting in check_prop Update formatting in chunk Update formatting in transpose Update formatting in bifurcate Update formatting in union_by Update formatting in initialize_list_with_range Update formatting in most_frequent
18 lines
430 B
Markdown
18 lines
430 B
Markdown
---
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title: sum_by
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tags: math,list,function,beginner
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---
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Returns the sum of a list, after mapping each element to a value using the provided function.
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Use `map()` with `fn` to map each element to a value using the provided function, use `sum()` to return the sum of the values.
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```py
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def sum_by(lst, fn):
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return sum(map(fn, lst))
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```
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```py
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sum_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda v : v['n']) # 20
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```
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