pluck 0.1

pluck: Quickly pluck “fields” from a list of values

pluck is the simplest way of plucking “fields” from an iterable of values. “Fields” are either item.field or item[field]. Pluck tries both, in that order. If nothing is found, and no default value is specified, it throws an exception.

Usage

The package consists of one module consisting of one function:

from pluck import pluck

pluck(iterable, key)

Or:

pluck(iterable, *keys)

Examples

A simple example first. Say you have a list of datetimes:

>>> from pluck import pluck
>>> dates = [
...     datetime(2012, 10, 22, 12, 00),
...     datetime(2012, 10, 22, 15, 14),
...     datetime(2012, 10, 22, 21, 44),
... ]
>>> pluck(dates, 'day')
[22, 22, 22]
>>> pluck(dates, 'hour')
[12, 15, 21]

It also works on dictionary-like access (__getitem__):

>>> objects = [
...      {'id': 282, 'name': 'Alice', 'age': 30, 'sex': 'female'},
...      {'id': 217, 'name': 'Bob', 'age': 56},
...      {'id': 328, 'name': 'Charlie', 'age': 56, 'sex': 'male'},
... ]
>>> pluck(objects, 'name')
['Alice', 'Bob', 'Charlie']
>>> pluck(objects, 'age')
[30, 56, 56]

You can also combine these into a single pluck:

>>> pluck(objects, 'name', 'age')
[('Alice', 30), ('Bob', 56), ('Charlie', 56)]

Defaults

You can specify default values, too. By default, pluck will throw an exception when a “field” does not exist. To instead fill these places with a default value, use this:

>>> pluck(objects, 'sex')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pluck.py", line 104, in pluck
      return list(ipluck(iterable, *keys, **kwargs))
  File "pluck.py", line 49, in getter
      raise ValueError('Item %r has no attr or key for %r' % (item, key))
  ValueError: Item {'age': 56, 'id': 217, 'name': 'Bob'} has no attr or key for 'sex'
>>> pluck(objects, 'sex', default='unknown')
['female', 'unknown', 'male']

When you specify multiple keys, you need to use the defaults keyword argument instead (note the plurality):

>>> pluck(objects, 'name', 'sex', defaults={'sex': 'unknown'})
[('Alice', 'female'), ('Bob', 'unknown'), ('Charlie', 'male')]

Iterator, rather?

Use ipluck if you’d rather wanna have an iterator.

pluck is equivalent to list(ipluck(...)).

History

0.1.0 (2012-10-22)

• Initial release.