Live updating graph from increasing amount of csv files - python-3.x

Question

I need to analyse some spectral data in real-time and plot it as a self-updating graph.
The program I use outputs a text file every two seconds.
Usually I do the analysis after gathering the data and the code works just fine. I create a dataframe, where each csv file represents a column. The problem is, with several thousands of csv files, the import becomes very slow and creating a dataframe out of all the csv files takes usually more than half an hour.
Below the code for creating the dataframe from multiple csv files.
''' import, append and concat files into one dataframe '''
all_files = glob.glob(os.path.join(path, filter + "*.txt")) # path to the files by joining path and file name
all_files.sort(key=os.path.getmtime)
data_frame = []
name = []
for file in (all_files):
creation_time = os.path.getmtime(file)
readible_date = datetime.fromtimestamp(creation_time)
df = pd.read_csv(file, index_col=0, header=None, sep='\t', engine='python', decimal=",", skiprows = 15)
df.rename(columns={1: readible_date}, inplace=True)
data_frame.append(df)
full_spectra = pd.concat(data_frame, axis=1)
for column in full_spectra.columns:
time_step = column - full_spectra.columns[0]
minutes = time_step.total_seconds()/60
name.append(minutes)
full_spectra.columns = name
return full_spectra
The solution I thought of was using the watchdog module and everytime a new textfile is created it gets appended as a new column to the existing dataframe and the updated dataframe is plotted. Because then, I do not need to loop over all csv files all the time.
I found a very nice example on how to use watchdog here
My problem is, I could not find a solution how after detecting the new file with watchdog, to read it and append it to the existing dataframe.
A minimalistic example code should look something like this:
def latest_filename():
"""a function that checks within a directoy for new textfiles"""
return(filename)
df = pd.DataFrame() #create a dataframe
newdata = pd.read_csv(latest_filename) #The new file is found by watchdog
df["newcolumn"] = newdata["desiredcolumn"] #append the new data as column
df.plot() #plot the data
The plotting part should be easy and my thoughts were to adapt the code presented here. I am more concerned with the self-updating dataframe.
I appreciate any help or other solutions that would solve my issue!