Tips and Tricks

Toolz functions can be combined to make functions that, while common, aren’t a part of toolz’s standard offerings. This section presents a few of these recipes.

• pick(allowlist, dictionary)

  Return a subset of the provided dictionary with keys contained in the allowlist.

  from toolz import keyfilter
  
  def pick(allowlist, d):
      return keyfilter(lambda k: k in allowlist, d)
  

  Example:

  >>> alphabet = {'a': 1, 'b': 2, 'c': 3, 'd': 4}
  >>> pick(['a', 'b'], alphabet)
  {'a': 1, 'b': 2}
  

• omit(denylist, dictionary)

  Return a subset of the provided dictionary with keys not contained in the denylist.

  from toolz import keyfilter
  
  def omit(denylist, d):
      return keyfilter(lambda k: k not in denylist, d)
  

  Example:

  >>> alphabet = {'a': 1, 'b': 2, 'c': 3, 'd': 4}
  >>> omit(['a', 'b'], alphabet)
  {'c': 3, 'd': 4}
  

• compact(iterable)

  Filter an iterable on “truthy” values.

  from toolz import filter
  
  def compact(iter):
      return filter(None, iter)
  

  Example:

  >>> results = [0, 1, 2, None, 3, False]
  >>> list(compact(results))
  [1, 2, 3]
  

• keyjoin(leftkey, leftseq, rightkey, rightseq)

  Inner join two sequences of dictionaries on specified keys, merging matches with right value precedence.

  from itertools import starmap
  from toolz import join, merge
  
  def keyjoin(leftkey, leftseq, rightkey, rightseq):
      return starmap(merge, join(leftkey, leftseq, rightkey, rightseq))
  

  Example:

  >>> people = [{'id': 0, 'name': 'Anonymous Guy', 'location': 'Unknown'},
                {'id': 1, 'name': 'Karan', 'location': 'San Francisco'},
                {'id': 2, 'name': 'Matthew', 'location': 'Oakland'}]
  >>> hobbies = [{'person_id': 1, 'hobby': 'Tennis'},
                 {'person_id': 1, 'hobby': 'Acting'},
                 {'person_id': 2, 'hobby': 'Biking'}]
  >>> list(keyjoin('id', people, 'person_id', hobbies))
  [{'hobby': 'Tennis',
    'id': 1,
    'location': 'San Francisco',
    'name': 'Karan',
    'person_id': 1},
   {'hobby': 'Acting',
    'id': 1,
    'location': 'San Francisco',
    'name': 'Karan',
    'person_id': 1},
   {'hobby': 'Biking',
    'id': 2,
    'location': 'Oakland',
    'name': 'Matthew',
    'person_id': 2}]
  

• areidentical(\*seqs)

  Determine if sequences are identical element-wise. This lazily evaluates the sequences and stops as soon as the result is determined.

  from toolz import diff
  
  def areidentical(*seqs):
      return not any(diff(*seqs, default=object()))
  

  Example:

  >>> areidentical([1, 2, 3], (1, 2, 3))
  True
  

  >>> areidentical([1, 2, 3], [1, 2])
  False