Dotted notation parser with pattern matching
Project description
Dotted
Sometimes you want to fetch data from a deeply nested data structure. Dotted notation helps you do that.
Let's say you have a dictionary containing a dictionary containing a list and you wish to fetch the ith value from that nested list.
>>> import dotted
>>> d = {'hi': {'there': [1, 2, 3]}}
>>> dotted.get(d, 'hi.there[1]')
2
Grammar
Dotted notation looks similar to python. Both dot fields and slot fields,
e.g. brackets, call __getitem__
internally. A dot field expects to see
a dictionary-like object. A slot field is biased towards sequences (like
lists, tuples, and strs) but can act on dicts as well. Dotted also supports
slicing notation as well as transforms discussed below.
Patterns
You can use dotted for pattern matching. You can match to wildcards or regular expressions.
>>> import dotted
>>> d = {'hi': {'there': [1, 2, 3]}, 'bye': {'there': [4, 5, 6]}}
>>> dotted.get(d, '*.there[2]')
(3, 6)
>>> dotted.get(d, '/h.*/.*')
([1, 2, 3],)
Dotted will return all values that match the pattern(s).
Slicing
Slicing is also supported. Dotted slicing works like python slicing and all that entails.
>>> import dotted
>>> d = {'hi': {'there': [1, 2, 3]}, 'bye': {'there': [4, 5, 6]}}
>>> dotted.get(d, 'hi.there[::2]')
[1, 3]
>>> dotted.get(d, '*.there[1:]')
([2, 3], [5, 6])
The '+' operator
Both slots and slices support the '+' operator which refers to the end of sequence. You may append an item or slice to the end a sequence.
>>> import dotted
>>> d = {'hi': {'there': [1, 2, 3]}, 'bye': {'there': [4, 5, 6]}}
>>> dotted.update(d, '*.there[+]', 8)
{'hi': {'there': [1, 2, 3, 8]}, 'bye': {'there': [4, 5, 6, 8]}}
>>> dotted.update(d, '*.there[+:]', [999])
{'hi': {'there': [1, 2, 3, 8, 999]}, 'bye': {'there': [4, 5, 6, 8, 999]}}
Transforms
You can optionally add transforms to the end of dotted notation. These will
be applied on get
and update
. Transforms are separated by the |
operator
and multiple may be chained together. Transforms may be parameterized using
the :
operator.
>>> import dotted
>>> d = [1, '2', 3]
>>> dotted.get(d, '[1]')
'2'
>>> dotted.get(d, '[1]|int')
2
>>> dotted.get(d, '[0]|str:number=%d')
'number=1'
You may register new transforms via either register
or the @transform
decorator. Look at transforms.py for preregistered.
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