clean_vtt.py

import webvtt
import pandas as pd

filename="en.vtt"
time_epsilon=pd.Timedelta('00:00:00.1')

vtt=webvtt.read(filename)

df=pd.DataFrame([[pd.to_datetime(v.start),
                  pd.to_datetime(v.end),
                  v.text.splitlines()[-1]]
                 for v in vtt]
                ,columns=["start","end","text"])
df=df.where(df.end-df.start>time_epsilon).dropna()
print("\n".join(df.text)) # if you need all transcript

clean_vtt2.py

import webvtt
# inpired by Terence Eden https://shkspr.mobi/blog/2018/09/convert-webvtt-to-a-transcript-using-python/


lines = []
starts = []
ends = []
for line in vtt:
    extend_text=line.text.strip().splitlines()
    repeat=len(extend_text)
    lines.extend(extend_text)
    starts.extend([line.start] * repeat)
    ends.extend([line.end] * repeat)

previous = None
new_lines=[]
new_starts=[]
new_ends=[]

for l,s,e in zip(lines,starts,ends):
    if l == previous:
        continue
    else:
        new_lines.append(l)
        new_starts.append(s)
        new_ends.append(e)
        previous = l
        
print("\n".join(new_lines)) # if you need all transcript