Usage

The gems module provides specialized data structures to augment development. It’s similar to the collections module, but contains different types of objects.

Currently, the following objects are available (this list will grow with time and feedback):

Name	Description
composite	JSON-like data structure for easy data traversal.
filetree	JSON-like data structure for easy filesystem traversal.

composite

The gems.composite object abstracts away the complexity associated with managing heavily nested JSON-based structures, allowing easier access to internal properties, and providing operators that work with the data in an intuitive way. Here is a simple example of how to use the composite type in a project:

>>> from gems import composite
>>>
>>> data = composite({
>>>     'one': 1,
>>>     'two': [1, 2, 3],
>>>     'three': ['one', 2, {'three': 'four'}],
>>>     'four': {'five': [6, 7, 8], 'nine': 10, 'eleven': 'twelve'}
>>> })
>>> data.four.five[1] == 6
True
>>> data.two[0] == 1
True

In the example above, an arbitrary data structure is provided as an argument to the composite object, and is transformed into an object where properties can be traversed more gracefully (syntactically). You can also load a composite object from a json or yaml file like so:

>>> from gems import composite
>>>
>>> with open('data.json', 'r') as fi:
>>>     data = composite.load(fi)
>>>
>>> print data.four.five[1]
6
>>>
>>> with open('data.yml', 'r') as fi:
>>>     data = composite.load(fi)
>>>
>>> print data.four.five[1]
6

Some of the main features of composite objects that make them particularly useful are operators for interacting with the structure. For instance, if two composite objects or a composite object and another similar type are added, you get a composite object as a result that combines the objects in an intuitive way:

>>> # using the 'data' object from above
>>> obj = data + {'five': 6}
>>> obj.five == 6
True
>>> obj.two === [1, 2, 3]
True

>>> obj = data + [1, 2, 3]
>>> obj[0].one.two[0] == 1
True
>>> obj[1][1] == 2
True

>>> data2 = composite([
    1, 2, 3, {'four': 5}
])
>>> obj = data2 + {'five': 6}
>>> obj[0][0] == 1
True
>>> obj[0][2].four == 5
True
>>> obj = data2 + ['seven', 8, 9]
>>> obj[4:6] == ['seven', 8]
True

Other operations like this also can be used with the composite object. For example:

>>> # using the 'data' object from above
>>> 'three' in data
True
>>> 7 in data.four.five
True
>>> data.four.five == [6, 7, 8]
True
>>> data == data2
False

Along with these operators, composite objects also extend set-based functionality for reducing data. For example:

>>> # initialize some data
>>> c1 = composite({
>>>     'one': 1,
>>>     'two': [1, 2],
>>>     'three': {'four': 5, 'five': 7},
>>>     'eight': 8
>>> })
>>> c2 = composite({
>>>     'one': 1,
>>>     'two': [1, 2, 3],
>>>     'three': {'four': 5, 'six': 7},
>>>     'eight': 9,
>>>     'nine': 10
>>> })
>>>
>>> # take the recursive intersection of the data structures
>>> print c1.intersection(c2)
{
    'one': 1,
    'two': [1, 2],
    'three': {'four': 5},
}
>>>
>>> # take the recursive difference of the data structures
>>> print c2.difference(c1)
{
    'two': [3],
    'three': {'six': 7},
    'eight': 9,
    'nine': 10
}
>>>
>>> # take the recursive union of the data structures
>>> print c1.union(c2)
{
    'one': 1,
    'two': [1, 2, 3],
    'three': {'four': 5, 'five': 7, 'six': 7},
    'eight': [8, 9],
    'nine': 10
}

Finally, you can write composite objects back to JSON files easily:

>>> # change the data in the object
>>> data.four.five = 2
>>>
>>> with open('newdata.json', 'w') as nd:
>>>     data.write(nd)

By default, this will sort keys and pretty-print to the file, but if you just want to print the raw json to file, use pretty=False.

filetree

Traversal of a filetree is typically a pain in python. You could use os.path.walk recursively to accomplish it, but there should be an easier way. That’s where the gems.filetree comes in handy. Here is an example of how to use the gems.filetree type in a project:

>>> from gems import filetree
>>>
>>> # mydir is a directory with the structure below
>>> ftree = filetree('mydir')
>>> print ftree
mydir/
     one/
        two.txt
        three.json
    two/
        three/
              four.txt
        five six/
                 seven.txt
        eight.config

The gems.filetree structure also allows for traversal of the file data like so:

>>> print data.one['two.txt']
/full/path/to/mydir/one/two.txt
>>>
>>> print data.two.three['four.txt']
/full/path/to/mydir/two/three/four.txt
>>>
>>> print data.two['five six']['eight.config']
/full/path/to/mydir/two/five six/eight.config

As you can see in the example above, using JSON-based access is much easier and cleaner than doing many os.path.join operations to create the full paths to objects on your filesystem. You can also create a json structure from the filetree:

>>> print data.json()
{
    "one": {
        "two.txt": "/path/to/mydir/one/two.txt",
        "three.json": "/path/to/mydir/one/three.json"
    },
    "two": {
        "three": {
            "four.txt": "/path/to/mydir/two/three/four.txt"
        },
        "five six": {
            "seven.txt": "/path/to/mydir/two/five six/seven.txt"
        },
        "eight.config": "/path/to/mydir/two/eight.config"
    }
}

Or, if you just want to see a list of all files in the filetree, you can do the following:

>>> print data.files()
'/path/to/mydir/one/two.txt'
'/path/to/mydir/one/three.json'
'/path/to/mydir/two/three/four.txt'
'/path/to/mydir/two/five six/seven.txt'
'/path/to/mydir/two/eight.config'

Finally, to prune the tree for specific files and create a new filetree object:

>>> newtree = data.prune(regex=".*.txt$")
>>> print newtree.files()
'/path/to/mydir/one/two.txt'
'/path/to/mydir/two/three/four.txt'
'/path/to/mydir/two/five six/seven.txt'