single

single(predicate=None)

Returns the only element in an Enumerable collection.

If a predicate is given, then it must be the only element in the collection that satisfies the condition. If the collection contains no elements that satisfy the given predicate then a NoElementsError is raised. If the collections contains 2 or more matching elements then a MoreThanOneMatchingElementError is raised.

This is an executing function.

Parameters

predicate : condition to satisfy as a lambda function. Optional.

Returns

The only element in the Enumerable collection that matches the given predicate.

Example

from py_linq import Enumerable

Enumerable([
    {'value': 1},
    {'value': 2},
    {'value': 3}
]).single(lambda x: x['value'] == 1)
# {'value': 1}

Enumerable([
    {'value': 1},
    {'value': 2},
    {'value': 3}
]).single()
# MoreThanOneMatchingElementError

Enumerable([]).single()
# raises NoElementsError