[Tutor] python scripts in HTML documents

[Erik Price]

On Sunday, May 19, 2002, at 10:34  AM, john public wrote:

> Can I insert Python code into an HTML document like I can insert a 
> piece of JavaScript code into an HTML document? JavaScript is a 
> scripting language, and Python is a scripting language and also more. 
> Yes?

Scripting languages are also called interpreted languages.  This is 
because you don't compile the code as a separate step, you just submit 
the code to an interpreter and the interpreter executes the appropriate 
actions based on the code.  Python works this way, as does JavaScript.

The difference between Python and JavaScript is that there is a 
JavaScript interpreter in most web browsers, but no Python interpreter 
that I have ever heard of.  JavaScript has somehow become something of a 
standard client-side scripting language for web pages, but Python (and 
PHP and Perl) is for the most part limited to performing server-side 
scripting.  For instance, you could create a Python script that 
generates a web page when the following HTTP request is made:

http://domain.com/page.py?article=11232

What this request would do is send a variable "article" whose value is 
"11232" to a script called "page.py" at URL "domain.com".  What 
"page.py" does with this variable could be anything, but possibly it 
could search a database for an article (using 11232 as the key of the 
article in the database), read the article, insert the contents of the 
article into a dynamically-generated string of HTML, and then send that 
HTML code (including the article) to your browser so that it looks like 
you have received a web page -- even though there may be no 
"traditional" web page whatsoever on that server (only scripts like this 
that imitate web pages by dynamically generating HTML from database 
content).

To get back to your question: if someone ever created a browser with a 
Python interpreter built in, then yes you could do the kinds of things 
that you do with JavaScript but in Python instead.  But I doubt that 
this will happen -- one of the nice things about JavaScript, from a 
security point of view, is that it is very limited in what it can and 
cannot do on the user's computer.  For instance, the JavaScript 
implementation in most modern browsers cannot read or write any files on 
a user's hard disk without some kind of permission on the part of the 
user.  This makes JavaScript a very safe scripting language from the 
perspective that it would be hard for a hacker or other malificant to do 
damage to someone using it.  And of course, you can always turn your 
browser's JavaScript interpreter off, which means that none of the 
JavaScript code will work.



Erik