nth

class iteration_utilities.nth(x)

Class that returns the n-th found value.

Parameters
nint

The index of the wanted item. If negative the last item is searched.

Note

This is the only parameter for __init__. The following parameters have to be specified when calling the instance.

iterableiterable

The iterable for which to determine the nth value.

defaultany type, optional

If no nth value is found and default is given the default is returned.

predcallable, optional

If given return the nth item for which pred(item) is True.

Note

pred=None is equivalent to pred=bool.

truthybool, optional

If False search for the nth item for which pred(item) is False. Default is True.

Note

Parameter is ignored if pred is not given.

retpredbool, optional

If given return pred(item) instead of item. Default is False.

Note

Parameter is ignored if pred is not given.

retidxbool, optional

If given return the index of the n-th element instead of the value. Default is False.

Returns
nthany type

The last value or the nth value for which pred is True. If there is no such value then default is returned.

Raises
TypeError :

If there is no nth element and no default is given.

Examples

Some basic examples including the use of pred:

>>> from iteration_utilities import nth
>>> # First item
>>> nth(0)([0, 1, 2])
0
>>> # Second item
>>> nth(1)([0, 1, 2])
1
>>> # Last item
>>> nth(-1)([0, 1, 2])
2

>>> nth(1)([0, 10, '', tuple(), 20], pred=bool)
20

>>> # second odd number
>>> nth(1)([0, 2, 3, 5, 8, 9, 10], pred=lambda x: x%2)
5

>>> # default value if empty or no true value
>>> nth(0)([], default=100)
100
>>> nth(-1)([0, 10, 0, 0], pred=bool, default=100)
10

Given a pred it is also possible to look for the nth False value and return the result of pred(item):

>>> nth(1)([1,2,0], pred=bool)
2
>>> nth(-1)([1,0,2,0], pred=bool, truthy=False)
0
>>> import operator
>>> nth(-1)([[0,3], [0,1], [0,2]], pred=operator.itemgetter(1))
[0, 2]
>>> nth(-1)([[0,3], [0,1], [0,2]], pred=operator.itemgetter(1), retpred=True)
2

There are already three predefined instances:

__call__(iterable[, default, pred, truthy, retpred, retidx])

Find the n-th element.

n

(int) The index to get (readonly).

New in version 0.6.