Develop Reference

Running a Python Script on a Website (in the background)

Firstly, apologies for the very basic question. I have looked into other answers but they haven't quite answered what I'm after. I'm confident designing a site in HTML/CSS and have very very basic knowledge of Python.
I want to run a very basic Python script on my website. It analyses tweets about a specific topic, and then posts a sentiment analysis score. I want it to run this sentiment analysis every hour and cache the score.
I have a working Python script which does this in Jupyter Notebook. Could you give me an overview of how I would make this script function online and cache the results? I've read into using Python web frameworks, but from my limited understanding, they seem like overkill?
Thank you for your help!

Could you give me an overview of how I would make this script function online
The key thing would be to uncouple the two parts of your system:
Producing the data
Showing it in a website.
So the first thing to do is have your sentiment-analysis script push its value to a database. The database could be something as simple as a csv file, or it could be a key/value store, or something like MySQL or CouchDB (or hundreds of other choices).
Over on the website you have to make a decision between:
Server-side
Client-side
If the former, you could program in Python if that is what you are most familiar with. Whatever language/framework combination you go for, there will an example tutorial of how to read a value from a database and display it: it is just about the most fundamental thing.
If client-side you will usually be programming in JavaScript. Again you need to choose a framework, but again you should easily be able to find a tutorial to follow.
(Unless you have a good reason to prefer server-side, such as familiarity with an existing framework, or security issues with accessing your database, I'd go with a client-side approach.)
I've read into using Python web frameworks... overkill?
Yes and no. You are going to need some kind of database, and some kind of framework. It would be good to understand the basics of web security, too. If the sentiment analysis is your major goal, all that is going to be a distraction, and it might be better to find a friend who already knows web programming to work with. Or just find a tutorial that is very close to what you want to do, and adapt that.
(P.S. I was going to flag your question as "too broad", but you did ask for an overview, so I hope this helps.)

Filling textfields on webserver with python?

iam relativ new to Python and a noob in programming.
I wonder if there is a way to fill textfields
on a website?
Iam thinking about writing an python application for linux terminals where the user input will be send to the website, placed in the right webforms and then prints the formatted output back in the linux terminal. Is this possible?
It would be nice if such a thing is possible in python since I am just learning it and I like it so far.
I also tried looking for related stuff but I don't know where to start. Found this page here which seems like the right direction but I am not sure:
https://pymotw.com/2/socket/tcp.html
Also this seems right (https://splinter.readthedocs.io/en/latest/) but I am not sure if I can get the new page contents back on the terminal.

Execute python functions and read variables from html

First off, I am very new to programming and I have a relatively basic understanding of python, and average understanding of html.
Using what I know in python, I am trying to create a basic strategy game, a bit like the likes of Age of Empires, or Command and Conquer, based on collecting resources and using it to build things, except using a simple text or button-clicking type interface. I can do a text interface fine, but its a bit boring, and I would like to use some images. I have had a 1 hour lecture on tkinter, but I have tried and failed to make anything remotely 'usable' from it. What I can do, is make decent looking html pages which would serve my purpose very well.
What I am wondering is if there is a simple way of executing python functions and calling/displaying python variables through a html page? The python functions do all the logic and present variables which represent current resource levels, production, storage capability, levels of buildings, etc. At the most basic level all I need is a way of displaying these variables, and having buttons which execute a function to say, upgrade a building, which recalculates production and all that, and returns the new set of values.
As a really simple example:
<p> Wheat production: *python integer representing production*</p>
<button type="button" onclick="*execute python variable*">Upgrade Wheat</button>
There would also, I imagine, be a need to somehow update the variables which are changed on the html page. So the button executes a function to upgrade wheat production, python now has a new value for the wheat production variable, and this needs to be updated on the page, whether this is automatic, or by some other method. I guess the simple way would be if pressing the button could also reload the page, but that seems a little clumsy.
Does anyone know of a simple way of doing this? Or perhaps a python library which might help me here?

Yes, there is a way of doing this.
There are two approaches to this. One is to have all the work done on the server, the other approach is to use Javascript.
The first approach is this: write a python script that generates your HTML. If you use Django, you will get a lot of work done for you, but you will also get a lot of stuff you don't want. Django does have a built-in template language. Django is beyond the scope of this answer. You will get to do exactly what you describe above; an example of a template might be <p> Wheat production: {{wheat_production}}</p> - your python code will set up a dict mydict={"wheat_production":10} and you will pass the name of your template file and the dict to a function which will spit out your page. You will also have to learn about HTML forms, if you haven't done so yet.
The other approach is to use Ajax - Javascript that, when your page is displayed (and, perhaps, when buttons are clicked, or at regular intervals) will send/receive some data to allow you to update your page. I suggest looking into JQuery to do some of the lifting for you. This means that you can update bits of the page without having to reload the entire thing. You will still have to write some code on the server to talk to the database, and send the output, usually as JSON, back to the client.
When writing this sort of thing, make sure all of your security is on the server side, and don't trust anything the user tells you. For example, if you store the number of gold pieces in a field on your form, it's going to take someone about 10 seconds to give themselves as much gold as they want. Similarly, if a player can sell a diamond for 20 gold pieces, make sure they have the diamond before giving them the gold pieces - you don't want to end up with a player with 1,000,000 gold pieces and negative a thousand diamonds. Javascript is 100% insecure, anything that Javascript can do, the player can also do.

Take a look at http://pyjs.org/
What is pyjs?
pyjs is a Rich Internet Application (RIA) Development Platform for
both Web and Desktop. With pyjs you can write your JavaScript-powered
web applications entirely in Python.
pyjs contains a Python-to-JavaScript compiler, an AJAX framework and a
Widget Set API. pyjs started life as a Python port of Google Web
Toolkit, the Java-to-JavaScript compiler.
You can compile Python programs to javascript, and also use their Python libraries to generate HTML. Here's an example from their getting started guide:
from pyjamas import Window
from pyjamas.ui import RootPanel, Button
def greet(sender):
Window.alert("Hello, AJAX!")
class Hello:
def onModuleLoad(self):
b = Button("Click me", greet)
RootPanel().add(b)

Create a 'single-serving site' with python

I want to make a Python script available as a service on the net. The script, which is my first 'proper' Python program, takes a txt file as argument and writes an image into the work directory. So:
How difficult is it for somebody who is new to Python and web development?
How much work is it?
Do I need a framework (Django, cherryPy, web2py)?
Are there good tutorials?
How do I avoid the server to be compromised?
What are my next steps?
==> What is the easiest way?
In the end it is enough, if it is a white page, with some text, and a button, which when clicked, opens a file dialog. After the txt is processed, the server should just return the image, which was written on the hard drive. Already I have access to a server which has Ubuntu installed through a friend.
[update]
Thanks for all your answers. After reading them I want to stress again, that I want to have it as minimal as possible. Srikar's suggestion sounds like the easiest one:
Put it in executable directory of your OS (commonly known as CGI
path). Provide a simple HTML form & upon form submission hit this
script which executes & returns back the image you want to display.
Any objections or comments? Do you know any tutorials for that?
[udpate2]
I found this SO answer: File Sharing Site in Python Is this a sensible approach?

It's not too difficult. Actually, it sounds like a good first project.
That too subjective to answer. An hour to days.
No, you don't need one, but I'd use one if I were you. They abstract away some of the stuff you really don't care about, and you'll learn a tool you can use again in the future.
Plenty. If you want a real rundown of how Python works for the web, read the HOWTO from Python.org. If you just want to learn how to do this one project, pick a framework and do their tutorial.
This question is so broad and complex that I'm not going to try to answer it. Search this site, or Google, for questions like that.
Your next step should be to pick a framework; I've used Django successfully. Just download it, follow the installation instructions, and work your way through their tutorial; it should tell you everything you need to know to do what you want. If you still have questions once you've learned how to do the basics, come back and ask again!
Edit: The answer to that other question will certainly work for you. There, they just receive a GET request and respond with data from a Python file. You need to receive a GET request, respond with an HTML page (easy enough), then respond to a POST request that includes an uploaded file (slightly more complicated) and run your python routine on the uploaded file and then respond with the created image (or a link to it).
Take a look at this page which includes a simple Python script to do file uploads. You should easily be able to modify it to do what you want.

How difficult is it for somebody who is new to Python and web development?
Depends on your level of knowledge.
How much work is it?
Depends on which method you choose to solve the problem.
Do I need a framework (Django, cherryPy, web2py)?
Not necessarily - you could get started by using the CGI (http://docs.python.org/library/cgi.html)
Are there good tutorials?
Yes, there are plenty. The Python docs are an excellent place to start.
How do I avoid the server to be compromised?
Again, depends on the method you choose to solve the problem, although there are commonalities.
What are my next steps?
Dare I say it again, choose a method, read the docs, have a play!

If its just as simple as you have described it. Then you might not even need Django. You could simply use CGI scripting. All of these design decisions, depend on whether
You need (or foresee) a SQL storage?
or a Content-Management-System?
Will you need multiple-user support?
Do you need tight security?
Do you need different privileges for different users?
Do you need an Admin to manage your site?
If the answer to above questions is atleast 60% correct, then you might consider Django. otherwise, just write a python script. Put it in executable directory of your OS (commonly known as CGI path). Provide a simple HTML form & upon form submission hit this script which executes & returns back the image you want to display. So, it all depends on the features you need...

In the end, I created what I needed with Flask.
They have a well documented pattern / tutorial on Uploading Files. The tutorial is understandable even for people with little python and web expericence.
To get a first working version it took me 2h and the resulting code was only 50 lines. This includes, starting the webserver, having a html file/form with file upload and serving a file back to the user.

What web programming languages are capable of making this web app?

I'm exploring many technologies, but I would like your input on which web framework would make this the easiest/ most possible. I'm currently looking to JSP/JSF/Primefaces, but I'm not sure if that is capable of this app.
Here's a basic description of the app:
Users log in with their username and password (maybe I can somehow incorporate OPENID)?
With a really nice UI, they will be presented a large list of questions specific to a certain category, for example, "Cooking". (I will manually compile this list and make it available.)
When they click on any of these questions, a little input box opens up below it to allow the user to put in a link/URL.
If the link they enter has the same question on that webpage the URL points to, they will be awarded one point. This question then disappears and gets added to a different page that has a list of all correctly linked questions.
On the right side of the screen, there will be a leaderboard with the usernames of the people with the top ten points.
The idea is relatively simple - to be able to compile links to external websites for specific questions by allowing many people to contribute.
I know I can build the UI easily with Primefaces. [B]What I'm not sure is if JSP/JSF gives the ability to parse HTML at a certain URL to see if it contains words.[/B] I can do this with python easily by using urllib, but I can't use python for web GUI building (it is very difficult). What is the best approach?
Any help would be appreciated!!! Thanks!

The best approach is whatever is best for you. If Python isn't your strength but Java is, then use Java. If you're a Python expert and know little Java, use Python.
There are so many resources on the Internet supporting so many platforms that the decision really comes down to what works best for you.

For starters, forget about JSP/JSF. This is an old combination that had many problems. Please consider Facelets/JSF. Facelets is the default templating language in the current version of JSF, while JSP is there only for backwards compatibility.
What I'm not sure is if JSP/JSF gives the ability to parse HTML at a certain URL to see if it contains words.
Yes it does, although the actual fetching of data and parsing of its content will be done by plain Java code. This itself has nothing to do with the JSF APIs.
With JSF you create a Facelet containing your UI (input fields, buttons, etc). Then still using JSF you bind this to a so-called backing bean, which is primarily a normal Java class with only one or two JSF specific annotations applied to it (e.g. #ManagedBean).
When the user enters the URL and presses some button, JSF takes care of calling some action method in your Java class (backing bean). In this action method you now have access to the URL the user entered, and from here on plain Java coding starts and JSF specifics end. You can put the code that fetches the URL and does the parsing you require in a separate helper class (separation of concerns), or at your discretion directly in the backing bean. The choice is yours.
Incidentally we had a very junior programmer at our office use JSF for something not unlike what you are requesting here and he succeeded in doing it in a short time. It thus really isn't that hard ;)

No web technology does what you want. Parsing documents found at certain urls is out of the scope of building web interfaces.
However, each of Java's web technologies will give you, without limits, access to a rich and varied (if not too rich and much too varied) set of libraries and frameworks running on JVM. You could safely say that if there is a library for doing something, there will be a Java version available. Downloading and parsing a document will not require more than what is available in the standard library (unless you insist on injecting your dependencies or crosscutting your concerns), so no problems with doing your project with JSP, or JSF/Primefaces, or whatever.
Since you claim to already know Python, and since you will have to add some HTML/CSS anyway, I suggest you try Django. It's dead simple, has a set of OpenID plugins to choose from, will give you admin interface for free (so you can prime the pump with the first set of links).