orient : string 
Series 
default is ‘index' 
allowed values are: {‘split','records','index'} 
DataFrame 
default is ‘columns' 
allowed values are: {‘split','records','index','columns','values'} 
The format of the JSON string 
split : dict like {index -> [index], columns -> [columns], data -> [values]} 
records : list like [{column -> value}, … , {column -> value}] 
index : dict like {index -> {column -> value}} 
columns : dict like {column -> {index -> value}} 
values : just the values array 
table : dict like {‘schema': {schema}, ‘data': {data}} describing the data, and the data component is like orient='records'. 
Changed in version 0.20.0

df = pd.DataFrame([['a', 'b'], ['c', 'd']],
  index=['row 1', 'row 2'],
  columns=['col 1', 'col 2'])
###########
split
###########
df.to_json(orient='split')
>'{"columns":["col 1","col 2"],
 "index":["row 1","row 2"],
 "data":[["a","b"],["c","d"]]}'
###########
index
###########
df.to_json(orient='index')
>'{"row 1":{"col 1":"a","col 2":"b"},"row 2":{"col 1":"c","col 2":"d"}}'
###########
records
###########
df.to_json(orient='index')
>'[{"col 1":"a","col 2":"b"},{"col 1":"c","col 2":"d"}]'
###########
table
###########
df.to_json(orient='table')
>'{"schema": {"fields": [{"name": "index", "type": "string"},
  {"name": "col 1", "type": "string"},
  {"name": "col 2", "type": "string"}],
 "primaryKey": "index",
 "pandas_version": "0.20.0"},
 "data": [{"index": "row 1", "col 1": "a", "col 2": "b"},
 {"index": "row 2", "col 1": "c", "col 2": "d"}]}'