Of course! VideoFileClip is a core class from the moviepy library, a fantastic Python module for video editing and processing. It's the primary tool you'll use to load, manipulate, and save video files.

Here’s a comprehensive guide covering everything from basic usage to common tasks.

What is VideoFileClip?

VideoFileClip is an object that represents a video file. When you create an instance of it, you load the video into memory (or stream it), allowing you to access its properties (like duration, size, frame rate) and perform operations (like cutting, adding effects, or extracting audio).

Installation

First, you need to install the moviepy library. It's highly recommended to also install imageio for image and video I/O, and ffmpeg, which moviepy uses as a backend for most of its heavy lifting.

# Install moviepy and its dependencies
pip install moviepy
# For better performance and format support, install ffmpeg
# On macOS (using Homebrew):
brew install ffmpeg
# On Ubuntu/Debian:
sudo apt-get update && sudo apt-get install ffmpeg
# On Windows (using Chocolatey):
choco install ffmpeg

Basic Usage: Loading and Saving a Video

This is the "Hello, World!" of video processing with VideoFileClip.

from moviepy.editor import VideoFileClip
# --- 1. Load the video ---
# Create a VideoFileClip object from a file path.
# Replace 'my_video.mp4' with the path to your video file.
try:
    video = VideoFileClip("my_video.mp4")
    # --- 2. Access video properties ---
    print(f"Duration: {video.duration} seconds")
    print(f"Size (WxH): {video.size}")
    print(f"Frames per second (FPS): {video.fps}")
    # --- 3. Perform an operation (e.g., cut a 10-second clip) ---
    # The .subclip() method takes start and end times in seconds.
    # The end time is exclusive.
    clip = video.subclip(5, 15) # Cuts from the 5th second to the 15th second.
    # --- 4. Save the modified video ---
    # The .write_videofile() method writes the clip to a new file.
    # The codec is important for compatibility. 'libx264' is a standard H.264 codec.
    clip.write_videofile("my_new_video.mp4", codec="libx264", audio_codec="aac")
except Exception as e:
    print(f"An error occurred: {e}")
finally:
    # --- 5. Close the clips ---
    # This is crucial to free up system resources (memory).
    if 'video' in locals():
        video.close()
    if 'clip' in locals():
        clip.close()

Core Methods and Properties

Here are the most common things you'll do with a VideoFileClip object.

Properties (Read-Only)

• video.duration: Length of the video in seconds (float).
• video.size: A tuple (width, height) of the video's dimensions.
• video.fps: Frames per second (float).
• video.reader: The underlying file reader object (advanced use).
• video.audio: An AudioClip object if the video has audio, otherwise None.

Methods

• video.subclip(t_start, t_end): [Most Important] Creates a new VideoFileClip containing only the portion from t_start to t_end (in seconds).
• video.resize(new_size): Creates a new clip with a different resolution. new_size can be a tuple (width, height) or a float for a scaling factor (e.g., 5 for half size).
• video.speedx(factor): Creates a new clip with its speed changed by factor. factor=2 is 2x speed, factor=0.5 is half speed.
• video.rotate(angle, unit='deg', resample='bicubic', expand=True): Rotates the clip. angle is in degrees by default.
• video.write_videofile(filename, fps=None, codec='libx264', audio_codec='aac', bitrate=None, **kwargs): Saves the clip to a file.
  • codec: Video codec. Common choices are 'libx264' (H.264), 'mpeg4'.
  • audio_codec: Audio codec. 'aac' is common for H.264.
  • bitrate: Sets the video bitrate (e.g., "5000k" for 5000 kbps).

Common Video Editing Tasks

Task 1: Trimming a Video

We've already seen this with subclip. You can chain it with other methods.

from moviepy.editor import VideoFileClip
# Load the video
video = VideoFileClip("input.mp4")
# Trim from 10 to 20 seconds, then resize to half its original size
short_and_small = video.subclip(10, 20).resize(0.5)
# Save the result
short_and_small.write_videofile("trimmed_resized.mp4")
# Close clips
video.close()
short_and_small.close()

Task 2: Adding Text to a Video

This requires the TextClip class.

from moviepy.editor import VideoFileClip, TextClip, CompositeVideoClip
video = VideoFileClip("input.mp4")
# 1. Create a TextClip object
# You can customize font, color, size, etc.
# Make sure you have a .ttf font file or use a default one.
text_clip = TextClip(
    "Hello, World!",
    fontsize=70,
    color='white',
    font='Arial-Bold' # Or path to a .ttf file
)
# 2. Position the text clip
# 'center' is a preset position tuple (width/2, height/2)
text_clip = text_clip.set_position('center').set_duration(video.duration)
# 3. Composite the original video and the text clip
final_clip = CompositeVideoClip([video, text_clip])
# 4. Write the result to a file
final_clip.write_videofile("video_with_text.mp4")
# Close clips
video.close()
text_clip.close()
final_clip.close()

Task 3: Combining (Concatenating) Videos

Use the concatenate_videoclips() function.

from moviepy.editor import VideoFileClip, concatenate_videoclips
# Load multiple video clips
clip1 = VideoFileClip("part1.mp4")
clip2 = VideoFileClip("part2.mp4")
clip3 = VideoFileClip("part3.mp4")
# Concatenate them in order
final_video = concatenate_videoclips([clip1, clip2, clip3])
# Add a transition between clips (optional)
# from moviepy.video.fx import all as fx
# final_video = fx.crossfadein(final_video, duration=1.0) # Fade in the whole video
final_video.write_videofile("combined_video.mp4")
# Close all clips
clip1.close()
clip2.close()
clip3.close()
final_video.close()

Task 4: Extracting Audio from a Video

The audio property gives you an AudioClip object, which you can save directly.

from moviepy.editor import VideoFileClip
video = VideoFileClip("my_video_with_sound.mp4")
# Get the audio clip
audio = video.audio
# Check if audio exists
if audio:
    # Save the audio to an MP3 file
    # You might need to install 'pydub' and 'ffmpeg' for MP3 support
    audio.write_audiofile("extracted_audio.mp3")
    print("Audio extracted successfully!")
else:
    print("The video has no audio track.")
# Close clips
video.close()
if audio:
    audio.close()

Important Best Practices

1. Always Close Your Clips! Video files are large and take up significant memory. Failing to close clips with .close() can lead to memory leaks and crashes in long-running scripts. The try...finally block is a great way to ensure this happens.

2. Use Context Managers (with statement) A more modern and robust way to handle resource cleanup is by using a context manager. MoviePy supports this for many of its objects.

   from moviepy.editor import VideoFileClip
   # The 'with' statement automatically calls .close() when the block is exited
   with VideoFileClip("my_video.mp4") as video:
       clip = video.subclip(5, 15)
       clip.write_videofile("my_new_video.mp4")
   # No need to call video.close() or clip.close() here!

3. Be Patient with write_videofile Encoding video is computationally expensive. A 30-second clip can take anywhere from a few seconds to several minutes to process, depending on your computer's CPU/GPU and the complexity of the