def read_mongo(db, collection, query={}, host='localhost', port=27017, username=None, password=None, no_id=True):
""" 从Mongo读取并存储到DataFrame """
#连接MongoDB
db = _connect_mongo(host=host, port=port, username=username, password=password, db=db)
#对特定的数据库和集合进行查询
cursor = db[collection].find(query)
#读取数据并构造DataFrame
df =  pd.DataFrame(list(cursor))
#删除MongoDB中主键_id
if no_id:
    del df['_id']
return df

query =  {"ans_count":{$gte:100}
read_mongo(mydb,collection,query = query, port=27017, username=None, password=None, no_id=True)

File "<ipython-input-85-41c57b2616f6>", line 1
query =  {"ans_count":{$gte:100}}
                    ^
    SyntaxError: invalid syntax

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-89-145be822c0ee> in <module>()
----> 1 read_mongo(mydb,collection,query = query, port=27017)

<ipython-input-18-abe74f552447> in read_mongo(db, collection, query, host, port, username, password, no_id)
     10     """ 从Mongo读取并存储到DataFrame """
     11     #连接MongoDB
---> 12     db = _connect_mongo(host=host, port=port, username=username, password=password, db=db)
     13     #对特定的数据库和集合进行查询
     14     cursor = db[collection].find(query)

<ipython-input-18-abe74f552447> in _connect_mongo(host, port, username, password, db)
      6     else:
      7         conn = MongoClient(host, port)
----> 8     return conn[db]
      9 def read_mongo(db, collection, query={}, host='localhost', port=27017, username=None, password=None, no_id=True):
     10     """ 从Mongo读取并存储到DataFrame """

/anaconda3/lib/python3.6/site-packages/pymongo/mongo_client.py in __getitem__(self, name)
   1321           - `name`: the name of the database to get
   1322         """
-> 1323         return database.Database(self, name)
   1324
   1325     def close_cursor(self, cursor_id, address=None):

/anaconda3/lib/python3.6/site-packages/pymongo/database.py in __init__(self, client, name, codec_options, read_preference, write_concern, read_concern)
    105         if not isinstance(name, string_type):
    106             raise TypeError("name must be an instance "
--> 107                             "of %s" % (string_type.__name__,))
    108
    109         if name != '$external':

TypeError: name must be an instance of str