File Downloads

Return files from your functions and users get automatic download buttons.

Basic Usage

from func_to_web import run
from func_to_web.types import FileResponse

def create_multiple_files(name: str):
    file1 = FileResponse(
        data=f"Hello {name}!".encode('utf-8'),
        filename="hello.txt"
    )
    file2 = FileResponse(
        data=f"Goodbye {name}!".encode('utf-8'),
        filename="goodbye.txt"
    )
    return [file1, file2]

run(create_multiple_files)

Key Features

• Single file: Return FileResponse(data=bytes, filename="file.ext")
• Multiple files: Return [FileResponse(...), FileResponse(...)]
• Any file type: PDF, Excel, ZIP, images, JSON, CSV, binary data, etc.
• Large files: Uses streaming - handles GB+ files efficiently
• Clean UI: List of files with individual download buttons
• Filesystem tracking: Metadata encoded in filenames (no database required)
• 1-hour retention: Files available for 1 hour from creation (hardcoded)
• Automatic cleanup: Files older than 1 hour removed every hour

Working with Libraries

Works with any library that generates files:

from func_to_web import run
from func_to_web.types import FileResponse
import io

# PDF generation
from reportlab.pdfgen import canvas

def create_pdf(title: str):
    buffer = io.BytesIO()
    pdf = canvas.Canvas(buffer)
    pdf.drawString(100, 750, title)
    pdf.save()
    return FileResponse(data=buffer.getvalue(), filename="document.pdf")

# Excel generation
import pandas as pd

def create_excel(rows: int):
    df = pd.DataFrame({'A': range(rows), 'B': range(rows)})
    buffer = io.BytesIO()
    df.to_excel(buffer, index=False)
    return FileResponse(data=buffer.getvalue(), filename="data.xlsx")

# ZIP files
import zipfile

def create_archive(file_count: int):
    buffer = io.BytesIO()
    with zipfile.ZipFile(buffer, 'w') as zf:
        for i in range(file_count):
            zf.writestr(f'file{i}.txt', f'Content {i}')
    return FileResponse(data=buffer.getvalue(), filename="archive.zip")

run([create_pdf, create_excel, create_archive])

Performance

• No size limits: Handles very large files (GB+) in streaming mode
• Constant memory usage: Regardless of file size
• Same efficiency as file uploads: 8MB chunks
• Filesystem-based: Metadata encoded in filenames (no database)
• Background cleanup: Non-blocking startup cleanup process

File Cleanup & Retention

Generated files have a simple 1-hour lifecycle:

1. Immediate availability: Files ready for download right after generation
2. 1-hour retention: Files automatically deleted 1 hour after creation (hardcoded, non-configurable)
3. Automatic cleanup: Cleanup runs on startup and every hour while server runs
4. No download tracking: Files expire based on creation time, not download time

Directory configuration:

# Default directories
run(my_function)
# Returned files stored in: ./returned_files

# Custom directory
run(
    my_function,
    returns_dir="/path/to/returns"
)

Auto-Healing

If a file is manually deleted from disk, the system automatically detects this when someone tries to download it and returns a "File expired" error.

What's Next?

You've completed all Output Types! Explore additional features.

Next category:

• Tables - Return tables from lists or DataFrames
• Multiple Outputs - Return multiple outputs from a single function