How to find names of all collections using PyMongo?

How to find names of all collections using PyMongo and find all fields in chosen collection ? I have name of database and name of chosen collection. (Scenario : user input name of database, need to find all collections and show in dropdown list, when user click on one item need to find all fields in that collection)

To find the collections, you can use collection_names() - https://pymongo.readthedocs.io/en/stable/api/pymongo/database.html#pymongo.database.Database.collection_names

Update:

The collection_names is deprecated from 3.7 onwards and been replaced by list_collection_names() - https://pymongo.readthedocs.io/en/stable/api/pymongo/database.html#pymongo.database.Database.list_collection_names

This is very simple. e.g.

import pymongo
import json

if __name__ == '__main__':
    client = pymongo.MongoClient("localhost", 27017, maxPoolSize=50)
    d = dict((db, [collection for collection in client[db].collection_names()])
             for db in client.database_names())
    print json.dumps(d)

result -> {"database1":["collection1","collection2"...], "database2": [...], ...}, like:

{"test": ["score", "test4", "test5", "test6", "test3", "test7", "user", "test2", "test8"],
 "testdb": ["test5", "test8", "test2", "test9", "test3", "test4", "test6", "test"],
 "local": ["startup_log"],
 "stackoverflow": ["questions"]}