Skip to main content
Help us improve PyPI by participating in user testing. All experience levels needed!

Plucks values from an iterable.

Project description

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

https://travis-ci.org/nvie/pluck.png

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 two functions:

from pluck import pluck, ipluck

ipluck is just the iterable version of pluck. Use it like this:

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:

>>> 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'

To instead fill these places with a default value, use this:

>>> pluck(objects, 'sex', default='unknown')
['female', 'unknown', 'male']

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

>>> 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:

>>> from pluck import ipluck
>>> ipluck(large_stream_of_items, 'name')
<itertools.imap object at 0x10c7515d0>

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

History

0.2 (2012-10-22)

  • Add Python 3 compatibility
  • Improve documentation

0.1 (2012-10-22)

  • Initial release.

Project details


Release history Release notifications

This version
History Node

0.2

History Node

0.1

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Filename, size & hash SHA256 hash help File type Python version Upload date
pluck-0.2.tar.gz (4.3 kB) Copy SHA256 hash SHA256 Source None Oct 22, 2012

Supported by

Elastic Elastic Search Pingdom Pingdom Monitoring Google Google BigQuery Sentry Sentry Error logging CloudAMQP CloudAMQP RabbitMQ AWS AWS Cloud computing Fastly Fastly CDN DigiCert DigiCert EV certificate StatusPage StatusPage Status page