Write string to file #17

gregnordin · 2024-11-29T06:47:54Z

gregnordin
Nov 29, 2024

Is there a way to write a string to a file with LTK? I can do it with pyscript (example below), but if it can be done with LTK, it would make it more convenient for the small app I plan to develop. I have written a finite element simulation tool that I am adapting to use TOML files to specify and control the simulation geometry and specifics. The small app I want to develop with LTK provides a user interface to set up the geometry and simulation details. As such it will need to read and write TOML files, which is why I ask about using LTK to write a string to a file, which is the last base capability that I need. If there isn't a way to do this with LTK, I'll plan on having part of the app use pyscript directly for this feature. Ultimately I would like to open source the whole simulation tool and TOML file setup UI app to benefit my corner of the scientific world.

index.html file with pyscript code to write to a string to a file:

# index.html
<!DOCTYPE html>
<html>
<head>
    <title>PyScript String Writer</title>
    <script defer src="https://pyscript.net/latest/pyscript.js"></script>
    <link rel="stylesheet" href="https://pyscript.net/latest/pyscript.css">
</head>
<body>
    <button id="saveButton">Save Example String</button>

    <py-config>
        packages = []
    </py-config>

    <py-script>
from js import document, window, Blob, URL, console
from pyodide.ffi import create_proxy

def write_string_to_file(content, filename):
    try:
        # Create a Blob containing the text
        blob = Blob.new([content], {type: 'text/plain'})
        
        # Create a URL for the Blob
        url = URL.createObjectURL(blob)
        
        # Create a temporary link element
        link = document.createElement('a')
        link.href = url
        link.download = filename
        
        # Append link to body, click it, and remove it
        document.body.appendChild(link)
        link.click()
        document.body.removeChild(link)
        
        # Clean up the URL
        URL.revokeObjectURL(url)
        
    except Exception as e:
        console.error(f"Error saving file: {str(e)}")

def save_example(event):
    # Example string
    my_string = """This is an example string
with multiple lines
of text content."""
    
    write_string_to_file(my_string, "example.txt")

# Add event listener to the save button
save_button = document.getElementById('saveButton')
save_button.addEventListener('click', create_proxy(save_example))
    </py-script>
</body>
</html>

laffra · 2024-11-29T09:50:09Z

laffra
Nov 29, 2024
Maintainer

I added a class method to ltk.File that makes downloading a file easier than the code above. Click the "load a file" link at LTK Kitchensink. It will upload a file to the browser and then download it directly using ltk.File.download. The file type is derived from the file itself, so it works for text and binary files, but you can also override the content type.

Also, check out the Python context manager used by ltk.File for creating the object URL and ensure the URL is always revoked.

0 replies

gregnordin · 2024-11-29T22:28:29Z

gregnordin
Nov 29, 2024
Author

Awesome, again! I've played around with ltk.File.download and gone through the relevant code. The context manager for object_url looks like it does the right thing and is working correctly in my tests. I created an example on pyscript.com in case it is helpful.

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