How to read multiple json files into pandas dataframe?

Change the last line to:

temp = temp.append(data, ignore_index = True)

The reason we have to do this is because the append doesn’t happen in place. The append method does not modify the data frame. It just returns a new data frame with the result of the append operation.

Edit:

Since writing this answer I have learned that you should never use DataFrame.append inside a loop because it leads to quadratic copying (see this answer).

What you should do instead is first create a list of data frames and then use pd.concat to concatenate them all in a single operation. Like this:

dfs = [] # an empty list to store the data frames
for file in file_list:
    data = pd.read_json(file, lines=True) # read data frame from json file
    dfs.append(data) # append the data frame to the list

temp = pd.concat(dfs, ignore_index=True) # concatenate all the data frames in the list.

This alternative should be considerably faster.