FLATTEN¶
Description¶
FLATTEN extracts values from a list.
Given a list of dictionaries and a key (or a tuple of keys), it returns a flat list of the values at that key across all
dictionaries.
If called with no second argument, it removes one level of nesting and returns a list.
Example with a single key¶
This extracts the value at "key" from each dictionary, returning ["a", "b"].
Example with multiple keys¶
FLATTEN([{"key": "a", "age": 25, "name": "Alice"}, {"key": "b", "age": 30, "name": "Bob"}], ("key", "name"))
This returns only the named keys from each dictionary:
Example without a key¶
This concatenates the sublists into a single list, returning ["a", "b", "c", "d"].
An element that is not itself a list is kept as one element, so a list that is already flat comes back unchanged and an
empty list returns an empty list.
JOIN, SUM and the other operators that read a
list of values flatten what you give them anyway, so you only need FLATTEN where the shape of the list itself
matters, such as the rows of a markdown_table.