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function get_file_version_v1

Maturity: 47

Generates a version string for static files based on their modification time, used for cache busting in web applications.

File:
/tf/active/vicechatdev/vice_ai/new_app.py
Lines:
90 - 102
Complexity:
simple

Purpose

This function provides a cache-busting mechanism for static files (CSS, JavaScript, images) in Flask applications. It returns a version string based on the file's last modification time, which can be appended to URLs as a query parameter. When the file changes, the version string changes, forcing browsers to fetch the updated file instead of using a cached version. Falls back to current timestamp if the file cannot be accessed.

Source Code

def get_file_version(filename):
    """Get version string for static files based on modification time"""
    try:
        # Try to get file modification time for cache busting
        file_path = os.path.join(app.static_folder, filename)
        if os.path.exists(file_path):
            mtime = os.path.getmtime(file_path)
            return str(int(mtime))
    except (OSError, AttributeError):
        pass
    
    # Fallback to current timestamp
    return str(int(time.time()))

Parameters

Name Type Default Kind
filename - - positional_or_keyword

Parameter Details

filename: The relative path/name of the static file within the Flask application's static folder. Should be a string representing the file path (e.g., 'css/style.css', 'js/app.js'). The function will join this with app.static_folder to get the full path.

Return Value

Returns a string representation of an integer timestamp. If the file exists and is accessible, returns the file's modification time as a Unix timestamp (seconds since epoch) converted to a string. If the file doesn't exist or cannot be accessed, returns the current time as a Unix timestamp string. This value is typically used as a version parameter in URLs (e.g., '/static/style.css?v=1234567890').

Dependencies

  • flask
  • os
  • time

Required Imports

import os
import time
from flask import Flask

Usage Example

from flask import Flask
import os
import time

app = Flask(__name__)

def get_file_version(filename):
    try:
        file_path = os.path.join(app.static_folder, filename)
        if os.path.exists(file_path):
            mtime = os.path.getmtime(file_path)
            return str(int(mtime))
    except (OSError, AttributeError):
        pass
    return str(int(time.time()))

# Usage in Flask route or template context
version = get_file_version('css/style.css')
static_url = f'/static/css/style.css?v={version}'

# Or register as template filter
@app.template_filter('file_version')
def file_version_filter(filename):
    return get_file_version(filename)

# Then in Jinja2 template:
# <link rel="stylesheet" href="{{ url_for('static', filename='css/style.css') }}?v={{ 'css/style.css'|file_version }}">

Best Practices

  • This function requires access to a Flask app instance with a configured static_folder attribute
  • The function gracefully handles missing files and permission errors by falling back to current timestamp
  • Best used as a Jinja2 template filter or context processor for automatic version string generation in templates
  • The returned version string should be appended to static file URLs as a query parameter (e.g., ?v=timestamp)
  • Consider caching the results of this function in production to avoid repeated file system calls
  • Ensure the static folder has appropriate read permissions for the application user
  • The fallback to current timestamp means every request will generate a new version if the file doesn't exist, which may not be ideal for production
  • For production environments with multiple servers, consider using a consistent versioning strategy (like git commit hash) instead of file modification time

Tags

cache-busting static-files versioning flask web-development file-system timestamp asset-management browser-cache

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