mirror of
https://github.com/kennethreitz-archive/ijson.git
synced 2026-06-05 23:50:18 +00:00
Kenneth Reitz
67 lines
1.9 KiB
ReStructuredText
67 lines
1.9 KiB
ReStructuredText
=====
|
|
ijson
|
|
=====
|
|
|
|
Ijson is a Python wrapper to `YAJL <http://lloyd.github.com/yajl/>`_ which is a
|
|
streaming SAX-like JSON parser. Ijson provides a standard Python iterator
|
|
interface for it.
|
|
|
|
|
|
Usage
|
|
=====
|
|
|
|
All usage example will be using a JSON document describing geographical
|
|
objects::
|
|
|
|
{
|
|
"earth": {
|
|
"europe": [
|
|
{"name": "Paris", "type": "city", "info": { ... }},
|
|
{"name": "Thames", "type": "river", "info": { ... }},
|
|
// ...
|
|
],
|
|
"america": [
|
|
{"name": "Texas", "type": "state", "info": { ... }},
|
|
// ...
|
|
]
|
|
}
|
|
}
|
|
|
|
Most common usage is having ijson yield native Python objects out of a JSON
|
|
stream located under a prefix. Here's how to process all European cities::
|
|
|
|
from ijson import items
|
|
|
|
f = urlopen('http://.../')
|
|
objects = items(f, 'earth.europe.item')
|
|
cities = (o for o in objects if o['type'] == 'city')
|
|
for city in cities:
|
|
do_something_with(city)
|
|
|
|
Sometimes when dealing with a particularly large JSON payload it may worth to
|
|
not even construct individual Python objects and react on individual events
|
|
immediately producing some result::
|
|
|
|
from ijson import parse
|
|
|
|
f = urlopen('http://.../')
|
|
parser = parse(f)
|
|
stream.write('<geo>')
|
|
for prefix, event, value in parser:
|
|
if (prefix, event) == ('earth', 'map_key'):
|
|
stream.write('<%s>' % value)
|
|
continent = value
|
|
elif prefix.endswith('.name'):
|
|
stream.write('<object name="%s"/>' % value)
|
|
elif (prefix, event) == ('earth.%s' % continent, 'end_map'):
|
|
stream.write('</%s>' % continent)
|
|
stream.write('</geo>')
|
|
|
|
|
|
Acknowledgements
|
|
================
|
|
|
|
Ijson was inspired by `yajl-py <http://pykler.github.com/yajl-py/>`_ wrapper by
|
|
Hatem Nassrat. Though ijson borrows almost nothing from the actual yajl-py code
|
|
it was used as an example of integration with yajl using ctypes.
|