[Tutor] Env Vars

[Lloyd Kvam]

Thanks for stepping in Danny, I got sidetracked by work :)

Kyle, I think your email client discards the indentation.  I
actually tested this code example.

Danny Yoo wrote:

> 
> On Wed, 3 Jul 2002, Kyle Babich wrote:
> 
> 
>>I copied and pasted exactly what you put and replaced the path to python.
>>It says there is a syntax error at import HTMLgen.
>>
> 
> Hi Kyle,
> 
> 
> Ah!  That's probably a typo in the code: the block between the 'try:' and
> the 'except:' needs to be indented.
> 
> 
> 
> 
>>Also, is all of that really necessary just to print one environment
>>variable?
>>
> 
> If we just want to print the environmental variable, we can do this:
> 
> ###
> import os
> print "Content-type: text/plain\n\n"
> print "The server is running", os.name
> ###
> 
> and for simple stuff, this should be perfectly sufficient.
> 
> 
> 
> 
> Lloyd was showing a "simple" example of using the HTMLgen module.
> There's a admittedly some overhead in actually using the module itself,
> but that overhead comes with an advantage: HTMLgen is taking care of
> tricky details that CGI programmers can overlook if they're not careful.
> 
> 
> Let's take a look at the brunt of the HTMLgen stuff:
> 
> 
>>>ostext = HTMLgen.Text( "The server is running %s" % os.name)
>>>
> 
> The first line is constructing a chunk of text.  This may seem simple
> enough to be silly:  why do we even need to process it with HTMLgen?
> 
> But then, HTMLgen is taking care of some details.  Specifically, it's
> automatically HTML-quoting special characters like apostrophies and
> less-than signs for us:
> 
> http://starship.python.net/crew/friedrich/HTMLgen/html/HTMLgen-Text.html
> 
> HTML doesn't allow certain characters in documents because, otherwise,
> they could be mistaking for HTML tags!  So although it might be overkill
> for something simple like printing out 'os.name', it becomes much more
> useful when we use it in more involving scripts, where we get our data for
> all sorts of places.
> 
> 
> 
> 
>>>doc.append(ostext)
>>>doc.write()
>>>
> 
> Note that HTMLgen does not automatically print stuff to screen, which also
> may seem somewhat Useless: We insert it into the document 'doc', but we
> have to call doc.write() to get it to actually print out to the user. Why
> not just print 'ostext' out using a simple 'print' statement like this?
> 
> ###
> print ostext
> ###
> 
> and be done with it?
> 
> 
> One reason for delaying the printing is because it's often efficient to
> "buffer" our output and send it off in one go, instead of in little
> chunks.  Buffering is a good thing for a few other reasons, and you'll
> learn about them as you program more CGI's.
> 
> (One reason is that delaying output allows us to forwards and redirects
> more easily, without worrying about what has been sent to the user's
> browser window already.)
> 
> 
> 
> Also, HTMLgen is not just for CGI's: it can used in automatically
> generating HTML documents to disk.  doc.write() can take in an optional
> 'filename' parameter:
> 
> http://starship.python.net/crew/friedrich/HTMLgen/html/index.html
> 
> so that the output is not to screen, but to a file.
> 
> 
> Please feel free to ask more questions.  Hope this helps!
> 
> 
> 
> _______________________________________________
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> 
> 


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Lloyd Kvam
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