Save to csv file with dataframe data obtained from for loop

Question

I am trying to save data from a dataframe built during a while loop. However, on the exit of the loop, the LPCCfeatextr comes out empty. How can I parse the LPCCfeatextrdf dataframe to be saved to a csv file correctly?

Here is my code:

LPCCfeatextr = []

# Remove csv file if it exists
with contextlib.suppress(FileNotFoundError):
    os.remove(filename2)

def extract_features(file_name):
    try:
        fs, sig = wavfile.read(file_name)
        lpcs_feat = lpc(sig=sig, fs=fs, num_ceps=num_ceps)
        File_name = file_name
        shape = lpcs_feat.shape
        pad_width = max_pad_len - lpcs_feat.shape[1]
        lpcs_feat = np.pad(lpcs_feat, pad_width=((0, 0), (0, pad_width)), mode='constant')

        LPCCfeatextr.append([File_name, shape, pad_width])
        LPCCfeatextrdf = pd.DataFrame(LPCCfeatextr, columns=['File_name', 'Shape', 'Pad_width'])
        df = pd.DataFrame(LPCCfeatextrdf)

    except Exception as e:
        print("Error encountered while parsing file: ", file_name)
        return None

    return lpcs_feat, LPCCfeatextrdf

# Convert into a Panda dataframe
LPCCfeatextrdf = pd.DataFrame(LPCCfeatextr, columns=['File_name', 'Shape', 'Pad_width'])

# dataframe from dictionary
df = pd.DataFrame(LPCCfeatextrdf)

df.to_csv(filename2, mode='a', index=False, header=True)