Ijson is a Python wrapper to YAJL which is a streaming SAX-like JSON parser. Ijson provides a standard Python iterator interface for it.
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>')Ijson was inspired by 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.