Python: Using Function, Append Row of Data Extracted From File to Existing Dataframe

I have a file in my directory. I read it in with Python and then extract certain information from the file to place inside a dataframe as a new row.

Next, I want to read in a second file ... do the same steps as above and append the extracted data as a new row below the original row.

This process will repeat for hundreds of files sitting in one directory.

The two files below are fed into the input_file parameter in my function.

File 1: frame_IceCat_Category_788.feather
File 2: frame_IceCat_Category_42.feather

Function:

def miss_val_df(input_file):
    
    read_df = feather.read_feather(input_file)
    read_df.shape
    
    perc_missing = (read_df.isnull().sum()*100) / len(read_df)
    missing_df = pd.DataFrame({'col_name': read_df.columns, 'percent_missing': perc_missing})
    avg_missing = np.average(missing_df['percent_missing'])

    missing_df_2 = pd.DataFrame({'filename': input_file, 'num_rows': read_df.shape[0], 'num_cols': read_df.shape[1], 'missing_data_%': avg_missing}, index=[0])
    missing_df_2 = missing_df_2.append(missing_df_2)
    
    return missing_df_2

Calling my function twice:

miss_val_df('frame_IceCat_Category_788.feather')
miss_val_df('frame_IceCat_Category_42.feather')

My output table is:

As you can see, the output table is wrong. It overwrote the data from my first file: "frame_IceCat_Category_788.feather"

What am I doing wrong? How do I fix the above code?