nineml.utility.filter_expect_single

nineml.utility.filter_expect_single(lst, func=None, error_func=None)

Find a single element matching a predicate in a list.

This is a syntactic-sugar function _filter and expect_single in a single call.

Returns:

expect_single( _filter(lst, func), error_func )

This is useful when we want to find an item in a sequence with a certain property, and expect there to be only one.

Examples:

>>> find_smith = lambda s: s.split()[-1] == 'Smith'
>>> filter_expect_single( ['John Smith','Tim Jones'], func=find_smith )  
'John Smith'