Pandas row to json

Extending the answer of @MrE, if you're looking to convert multiple columns from a single row into another column with the content in json format (and not separate json files as output) I've had speed issues while using:

df['json'] = df.apply(lambda x: x.to_json(), axis=1)

I've achieved significant speed improvements on a dataset of 175K records and 5 columns using this line of code:

df['json'] = df.to_json(orient='records', lines=True).splitlines()

Speed went from >1 min to 350 ms.

Looping over indices is very inefficient.

A faster technique:

df['json'] = df.apply(lambda x: x.to_json(), axis=1)

Pandas DataFrames have a to_json method that will do it for you: http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.to_json.html

If you want each row in its own file you can iterate over the index (and use the index to help name them):

for i in df.index:
    df.loc[i].to_json("row{}.json".format(i))