Fixing WebVTT Times with Python

See Python: Tips and Tricks for similar articles.

Every once in a while, we need to make an edit to a video for which we already have closed captioning. If the edit affects the length of the video; for example, if we removed or added a segment to the video; then we will also need to edit the WebVTT file. Doing so manually is a pain, so I created a short Python function for handling this.

Here is the function:

from datetime import datetime, timedelta
def fix_vtt_times(vtt_input, seconds):
    """Fixes times in WebVTT by adding the passed-in seconds to all the timestamps.

        vtt_input (str): The text of the WebVTT
        seconds (float): The seconds to add. Use negative number to subtract.
    td = timedelta(seconds=seconds)
    dt_format = "%H:%M:%S.%f"
    vtt_output = ""

    for line in vtt_input.splitlines():

        if "-->" not in line:
            # This line doesn't have times. Just append it as is.
            vtt_output += line + "\n"

        start, end = line.split(" --> ")
        start = start.strip()
        end = end.strip()

        start_time_fixed = datetime.strptime(start, dt_format) + td
        end_time_fixed = datetime.strptime(end, dt_format) + td

        start_time = start_time_fixed.strftime(dt_format)
        end_time = end_time_fixed.strftime(dt_format)

        vtt_output += f"{start_time} --> {end_time}\n"

    return vtt_output

To use it, pass in the portion of the WebVTT content that you need to update and the number of seconds to add (or subtract). For example:

vtt = """00:00:46.750 --> 00:00:51.760
This is the result of launching our file in the Chrome browser.

00:00:51.760 --> 00:00:56.830
Notice that h1 renders a larger font in h2,

00:00:56.830 --> 00:01:01.420
and h2 renders a larger font than h3, and so on"""


fixed_text = fix_vtt_times(vtt, seconds)

After running this, fixed_text will contain:

00:00:40.450000 --> 00:00:45.460000
This is the result of launching our file in the Chrome browser.

00:00:45.460000 --> 00:00:50.530000
Notice that h1 renders a larger font in h2,

00:00:50.530000 --> 00:00:55.120000
and h2 renders a larger font than h3, and so on

Notice that all the timestamps have had 6.3 seconds subtracted from them.

Written by Nat Dunn. Follow Nat on Twitter.

Related Articles

  1. Fixing WebVTT Times with Python (this article)
  2. Using Python to Convert Images to WEBP
  3. Scientific Notation in Python
  4. Understanding Python’s __main__ variable
  5. Converting Leading Tabs to Spaces with Python
  6. pow(x, y, z) more efficient than x**y % z and other options
  7. A Python Model for Ping Pong Matches
  8. Bulk Convert Python files to IPython Notebook Files (py to ipynb conversion)
  9. Python’s date.strftime() slower than str(), split, unpack, and concatenate?
  10. Basic Python Programming Exercise: A Penny Doubled Every Day
  11. Bi-directional Dictionary in Python
  12. How to find all your Python installations on Windows (and Mac)
  13. Associate Python Files with IDLE
  14. Change Default autosave Interval in JupyterLab
  15. Python: isdigit() vs. isdecimal()
  16. Python Clocks Explained
  17. Python Color Constants Module
  18. Maximum recursion depth exceeded while calling a Python object
  19. When to use Static Methods in Python? Never
  20. Finally, a use case for finally – Python Exception Handling
  21. Creating an Email Decorator with Python and AWS
  22. Python Coding Challenge: Two People with the Same Birthday
  23. How to Create a Simple Simulation in Python – Numeric Data
  24. Collatz Conjecture in Python
  25. Simple Python Script for Extracting Text from an SRT File
  26. Python Virtual Environments with venv
  27. Mapping python to Python 3 on Your Mac
  28. How to Make IDLE the Default Editor for Python Files on Windows
  29. How to Do Ternary Operator Assignment in Python
  30. How to Convert Seconds to Years with Python
  31. How to Create a Python Package
  32. How to Read a File with Python
  33. How to Check the Operating System with Python
  34. How to Use enumerate() to Print a Numbered List in Python
  35. How to Repeatedly Append to a String in Python
  36. Checking your Sitemap for Broken Links with Python
  37. How to do Simultaneous Assignment in Python
  38. Visual Studio Code - Opening Files with Python open()
  39. How to Slice Strings in Python
  40. How Python Finds Imported Modules
  41. How to Merge Dictionaries in Python
  42. How to Index Strings in Python
  43. How to Create a Tuple in Python