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JSON file as a database

Project description

========
jsondb
========

Off-memory json for large data that does not fit the memory.

![Build Status](https://secure.travis-ci.org/shaung/jsondb.png?branch=develop)


Installation
----------------------
To install, simply run ::

python setup.py install


Getting started
----------------------

To create a db: ::

import jsondb

# Create from an empty dict (the default)
db = jsondb.create({})

# Or a list / tuple
db = jsondb.create([])


to create from an existing JSON file: ::

db = jsondb.from_file(json_file_path)
# file-like objects are accepted as well
db = jsondb.from_file(open(json_file_path, 'rb'))

Now add some data to the db and access them:

db['name'] = 'foo'
assert db['name'] == 'foo'

db['items'] = []
for i in range(3):
db['items'].append({
'id' : i,
'name': chr(97 + i),
})

assert db['items'][0]['id'] == 0
assert len(db['items']) == 3

assert db.get('nonexists', 'notfound') == 'notfound'

It works like an ordinary dict / list,
but to get its value, use the `data()` method:

# => 'foo'
print db['name'].data()

# Get the data
assert db.data() == {
'name' : 'foo',
'items': [
{'id' : 0, 'name' : 'a'},
{'id' : 1, 'name' : 'b'},
{'id' : 2, 'name' : 'c'},
]
}


Querying
----------------------

jsondb also supports complex queries, in a syntax based on JSONPath,
which is described here: http://goessner.net/articles/JsonPath/

`db.query` returns a `QueryResult` object which is iterable.

results = db.query('$.items.name')

# Iterating the query result
# => "a b c"
for x in results:
print x.data(),

To fetch all the value of the result,

# => ['a', 'b', 'c']
print rslt.values()

To fetch only one value,

# fetch one result
assert db.query('$.name').getone() == 'foo'
# => 'foo'
db.query('$.name').getone().data()

Example of more complex queries:

# Conditonal query
# => 'b'
print db.query('$.items[?(@.id = 1)].name').getone().data()

# slicing
# => ['a', 'b']
print db.query('$.items[:-1].name').values()


Persistence
----------------------

All the data is stored on the disk.
In the current implementation, data is saved as a sqlite database,
but supports for other DBMS are on the table.

both of `create` and `from_file` accept a `url` parameter,
indicating where to store the data:

db = jsondb.create({}, url='path/to/filename.db')
# which is equal to
db = jsondb.create({}, url='sqlite3://path/to/filename.db')

When not specified, a temporary file will be created in `/tmp` by default.

To make sure all the changes made to db being saved to the file,

db.save()

And when not needed anymore, remember to close it:

db.close()

Or use context manager:

with jsondb.create(url='path/to/filename.db') as db:
# do all the work here

To load an existing jsondb file later,

db = jsondb.load('path/to/filename.db')


License
----------------------

Released under the BSD license.

Project details


Release history Release notifications

This version
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0.1.2

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0.1.1

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