CherryPicker objects navigate your data by the following rules:

You apply filters to your data by providing predicates in parentheses after you have navigated to the data you want, for example:

>>> picker = CherryPicker(data)
>>> picker(name='Alice')
<CherryPickerIterable(list, len=1)>

…applied the predicate name='Alice' to the root data node. There were twelve items in the data that matched this filter. To see the actual data that was extracted, use the cherrypicker.CherryPicker.get() method:

>>> picker(name='Alice').get()
[{'name': 'Alice', 'age': 20}]

Filters behave slightly differently depending on what type of data you have at the point you apply them:

  • If the data is dict-like, each predicate will be applied to the value obtained by the key matching the predicate parameter. In the example above, the value for the key name will be checked, and if it is 'Alice', the filter has passed and the object will be returned. If the filter fails, the default item (which defaults to a leaf containing None) is returned instead.
  • If the data is list-like, the filter will be applied to each child. A new list-like node will be returned containing only the matching items.

Combining predicates

Multiple predicates can be applied in a single filter. The how parameter determines the logic used to combine them. If how is 'all' (which is the default), all predicates must match. If how is 'any', only one predicate needs to match for the filter to pass.

Types of predicate

The value supplied for each predicate term determines the kind of test that is performed:

  • If the predicate is a string, one of the following checks will be done:
    • If allow_wildcards=True and the string contains a wildcard character as defined by fnmatch.fnmatchcase(), then a wildcard match is performed.
    • If case_sensitive=False, a case-insensitive string comparison will be made.
    • If regex=True then the string will be compiled into a regular expression. A re.fullmatch() test will be performed. If case_sensitive is also False, the regex test will be case-insensitive.
    • Otherwise, only an exact match is accepted.
  • If the predicate is a compiled regular expression pattern, a re.fullmatch() test will be performed.
  • If the predicate is a callable function or lambda, the function will be applied to the value being tested. This function should take in a single parameter (the value) and return something that evaluates to True or False.


CherryPickerTraversable.filter(how='all', allow_wildcards=True, case_sensitive=True, regex=False, opts=None, **predicates) → cherrypicker.traversable.CherryPickerTraversable[source]

Return a filtered view of the child nodes. This method is usually accessed via CherryPicker.__call__()

For an object with a mappable interface, this will return the object itself if it matches the predicates according to the rules specified.

For an object with an iterable but not a mappable interface, a collection of child objects matching the predicates according to the rules specified will be returned.

This method is not implemented for leaf nodes and will cause an error to be raised.


Find any items with a name of Alice:

>>> picker(name='Alice')

Find any items with a name of Alice and an age of 20:

>>> picker(name='Alice', age=20)

Find any items with a name of Alice or an age of 20:

>>> picker(name='Alice', age=20, how='any')

Find any items with a name of Alice and an age of 20 or more:

>>> picker(name='Alice', age=lambda a: a >= 20)

Find any items with a name beginning with Al:

>>> picker(name='Al*')

Find any items with a name beginning with Al or al:

>>> picker(name='Al*', case_sensitive=False)

Find any items with a name of Al*:

>>> picker(name='Al*', allow_wildcards=False)

Find any items with a name matching a particular pattern (these two lines are equivalent):

>>> picker(name=r'^(?:Alice|Bob)$', regex=True, case_sensitive=False)
>>> picker(name=re.compile(r'^(?:Alice|Bob)$', re.I))
  • how (str.) – The rule to be applied to predicate matching. May be one of (‘all’, ‘any’).
  • allow_wildcards (bool, default = True.) – If True, special characters (*, ?, []) in any string predicate values will be treated as wildcards according to fnmatch.fnmatchcase().
  • case_sensitive (bool, default = True.) – If True, any comparisons to strings or uncompiled regular expressions will be case sensitive.
  • regex (bool, default = False.) – If True, any string comparisons will be reinterpreted as regular expressions. If case_sensitive is False, they will be case-insensitive patterns. For more complex regex options, omit this parameter and provide pre-compiled regular expression patterns in your predicates instead. All regular expressions will be compared to string values using a full match.
  • predicates (str, regular expression or Callable.) – Keyword arguments where the keys are the object keys used to get the comparison value, and the values are either a value to compare, a regular expression to perform a full match against, or a callable function that takes a single value as input and returns something that evaluates to True if the value passes the predicate, or False if it does not.

If this is a mappable object, the object itself if it passes the predicates. If not and this is an iterable object, a collection of children that pass the predicates.

Return type: