Single positional indexer is out-of-bounds error reading from CSV

Question

I'm attempting to read a .csv and write a new column. Whenever I call the function add(), the index error appears on Line 7.

def add():
    data = pd.read_csv('log.csv')
    for file in os.listdir('.'):
        if 'log' in file:
            continue
        df = pd.read_csv(open(file))
        val = data.loc[data['Num'] == file.split('.csv')[0], 'SAT'].iloc[0]
        ########more code using val#############
add()