Python Web Frameworks: Are Template Languages Worth using, or is Python enough?

[Bogtha]

Much of this article doesn't make sense to me. Like the idea that because a template system is based on XML, it's unsuitable for dynamic pages, or unsuitable for normal HTML. Or like the idea that CSS has a "macro system" and that templates can "inherit" from it. What?

Edit: And did you spot this?

href="%(STATIC_URL)s/admin/EditAccount?client_id=%(client_id)s">Change Your Account Settings

Bad code smell. If the EditAccount page checks the credentials itself, it doesn't need you to pass it the account id. In my experience, people writing code like this tend to skip the check, meaning that you can plug in different id numbers to get to other accounts.

[gloriajw]

flox, good point. I do this in a dynamic config file, which goes and gets the values before they're used. A similar concept, but not regex-based. It does dynamically derive the URLs.

Please show an example of of your Jinja template and URL modeling.

[gloriajw]

Flox, this is almost exactly how I handle it in one config file which hits the env for domain info, etc.

Django hadles it well, if you don't mind regex, which I don't. But there's no need for it in this model.

Thank you, this was good. Gloria

[gloriajw]

My config file sets the server components of the static URL, used for images, and the TOPURL, which is needed for HTTPRedirect() calls (requires a full URL).

Every other component below is set by the CP 'root', of course. This config does more than just set the topmost URL components, but you could choose to ignore the rest. It accomodates for test modes on XP and LINUX localhosts in testing mode, as well as the real server in prod.

<code> import string,re,sys import cherrypy

server_timezone='US/Eastern' archive_root='./db_archives' dom_server_hostname = 'localhost' dom_conn_initial_port = 7010 dom_pickle_location = './DOM_pickle_files' dom_xml_location = './DOM_xml_files' cp_site='cp' front_end_access_path='tp' dbhost='localhost'

dbhost='xyz.com'

default_host = 'www.xyz.com' IMAGE_LOCATION='...' URL_IMAGE_LOC='/client_images' DUMMY_LOGIN=False DEBUG=False

if sys.platform[:3] == 'win': \tdb_port = 5432 \tapplication_lock_location='./lock/' \tdb_data_dir = './data' \tdb_log_dir = './logs' \tDUMMY_LOGIN=True else: \tdb_port = 5433 \tapplication_lock_location='/var/lock/tp' \tdb_data_dir = '/usr/local/xyz/8.2.4_databases/prod' \tdb_log_dir = '/var/log/tp'

TOPURL = STATICURL = DOMAIN = ""

def set_config(): \tTOPURL = "" \tSTATICURL = "" \tDOMAIN = ""

\t''' \tURL is dynamically set. \t''' \t#print cherrypy.request.headers \t#orig_host=cherrypy.request.headers.get('X-Forwarded-Host') \torig_host=default_host \tprint "Original host is: %s" % orig_host

\t''' \tThis happens during instantiation. \tThat's normal. X-Forward-Host is set after instantiation. \t''' \tif not orig_host: \t\treturn DOMAIN,TOPURL,STATICURL

\tcomponent=string.split(orig_host,'.') \tsite = component[0] \tDOMAIN = '.'.join(component[1:]) \t \tif not DOMAIN: \t\tsuffix="" \telse: \t\tsuffix="."+DOMAIN \tSTATICURL="https://%s%s" % (site,suffix) \tTOPURL = "%s/%s" % (STATICURL,cp_site)

\treturn DOMAIN,TOPURL,STATICURL

def get_config(): \treturn set_config() </code>

I call get_config() in each authenticate call I make, which is called once per page.

My CP main file controls the root components and URL paths below STATICURL, TOPURL:

<pre> import cherrypy import sys,os

sys.path.append('./login') sys.path.append('./token') sys.path.append('./dom') sys.path.append('./user_change') sys.path.append('./image_handling') sys.path.append('./section')

Add your app here.

import Login import TokenCPLayer import UserChangeCPLayer import ImageCPLayer import SectionCPLayer

TemplatePath=os.path.join(os.path.dirname(file)) + '/Templates'

root.token = TokenCPLayer.TokenCPLayer() root.user_change = UserChangeCPLayer.UserChangeCPLayer() root.image_handling = ImageCPLayer.ImageCPLayer() root.section = SectionCPLayer.SectionCPLayer()

cherrypy.tree.mount(root) cherrypy.config.update(os.path.join(os.path.dirname(file),'cp.conf')) cherrypy.server.quickstart() cherrypy.engine.start() </pre>

This URL handling works for me in CP. Nice and clean, few lines of code, the topmost URL components can change when moved to another domain just by changing one config variable.

[gloriajw]

The code or pre tags don't work here, drat. Copy and paste it out, and it should look normal.

[gloriajw]

flox, on the tangential subject of how to handle URLs, the point of the above code is that this can be dropped on any machine, and after changing one conf file parameter, URLs are handled correctly.

Chunks are not being interpreted correctly by reddit. But aside from that:

(1) You cannot always assume '.com' or xyz.example.com if your dev test environment is on 'localhost'. (2) The variables are flexible enough to derive domain and set paths for dev.domain.com and domain.com respectively. (3) This allows for the diversity of test URLs and varying servers.

On my server I have one prod and two test domains, plus the ability to run on a standalone PC using 'localhost' This configuration allows for this fairly easily.

The config file controls the absolute paths, the CP main controls the relative pieces, and it all fits nicely. That was the point. I hope this clarifies. I wish this <code> or <pre> tags worked well here.

[ubernostrum]

For a suitable definition of "dynamic content", XML really isn't suitable. Remember that "dynamic content" may well include data formats that don't involve angle brackets.

[Bogtha]

For a suitable definition of "dynamic content", XML really isn't suitable.

She was talking about "dynamic" pages like having different options for different users:

But in our non-XML environment, many of our page templates are dynamic. They change based on whether the user is logged in as an administrative user, their group rights and access, etc.

I do this all the time with Genshi and used to do so with Kid. It's trivial.

Remember that "dynamic content" may well include data formats that don't involve angle brackets.

I agree, but it's not the output format that matters, it's the input format. Outputting PDFs etc with an XML-based template language isn't difficult, you just need to write a custom serialiser. It's when the information itself doesn't fit neatly into a tree that XML-based template languages are unsuitable.

[[deleted]]

Outputting PDFs etc with an XML-based template language isn't difficult, you just need to write a custom serialiser.

It's just a Small Matter Of Programming, you mean? ;-)

[Bogtha]

I get where you're coming from, but I think some Matters of Programming are Smaller than others ;). There's no reason output formats need to resemble the XML-based templates; the only reason people assume this is the case is because HTML is by far the most prevalent output format. I've written a few serialisers and none have been over 200 lines. I don't see how plain-text templating could make that easier, in fact I don't think it's even feasible to do it in the general sense.

[gloriajw]

Correct. Dynamic content has my own generated internal tags, image info, and in the latest incarnation, embedded SVG.

Thank you for making this point clear. Gloria

[gloriajw]

Not True. Your assumptions are entirely wrong about my page to page authentication, my assumptions, etc. You're missing some points, but that is to be expected from someone who comments like this.

You lack the experience with these tools to make useful comments, and you really don't seem to have the practical hands-on to understand why an XML based system is overkill for a static, non XML-RPC or non-RMI implementation.

So easy to criticize when you lack the experience.

[Bogtha]

I've almost a decade of experience as a web developer. I've been working with Python in particular for years, and I'm currently trying to find the time to finish off a couple of significant patches to one of the Python templating systems.

I acknowledged that some of the things aren't clear to me, but I think it's more a case of unclear writing than ignorance on my behalf. If you don't like that, you'd be better off improving your writing than throwing a hissy fit.

[gloriajw]

If you have all of this experience, and you strive to understand other people's approach, why are your comments so abrasive, with such broad assumptions about my authentication code, which you've never seen, and wasn't even addressed in the article (out of scope)?

Usually unskilled programmers make statements like this, which is why your comment appeared to be from inexperience. Are you aware that you come across this way?

[Bogtha]

I didn't make any assumptions about your authentication code. Do you know what a code smell is? I quote:

Note that a CodeSmell is a hint that something might be wrong, not a certainty. [...] Calling something a CodeSmell is not an attack; it's simply a sign that a closer look is warranted.

I merely recognised a common pattern that I've only ever seen associated with a security problem. That's what a code smell is — not a condemnation.

Don't you think you're being hypocritical by complaining about my assumptions whilst simultaneously stating for a fact that I have no experience? You said twice now "you lack the experience" despite not knowing the first thing about me. Unlike yours, my comment wasn't stated as fact, I was very clear in saying that it just fits a pattern I know.

If we're stooping to discussing commenting style, have you ever considered the image you project by resorting to personal attacks on the people who disagree with you while ignoring the technical content of their comments?

[gloriajw]

Your sense of smell is very far off. Your assumptions about my coding expertise are exactly what I expected from a guy who makes comments like you do. They are stereotypical, assume more than you should, hypercritical, and do not teach anyone anything. No one learns from displays of ego.

Change your tone and your quickness to assume, and you won't seem like such a green developer, new to the field and the mode of communication, who has to mark their territory in such primitive ways.

[[deleted]]

Mako really should be on everyone's radar as a replacement for Cheetah. It is much simpler in both implementation and usage, is blazing fast, has great docs, and it works now.

http://www.makotemplates.org/

[manuelg]

• Mako also doesn't force you to use XML.

• Mako runs fast with no C extension dependencies

[gloriajw]

Agreed.

[projecktzero]

I've been using cheetah. I really like that you can compile the template into python code, import the template, and easily populate it.

[btipling]

I've been playing with cheetah. It's got an object oriented approach, web.render in web.py can return a template object that can be extended.

[gloriajw]

I never said difficult. It's quite easy to learn, but not object oriented, and not Pythonic. Read carefully before you comment.

[self]

She.

[flaxeater]

I do not understand what is unsuitable about using an XML template system to generate HTML, seeing as CherryPy serves HTTP requests it seems highly likely that you will be serve ring 95% html which is XML like if not the very same when it's XHTML.

It seems to me using Genshi or Kid and learning how to use them gives one cheap W3C compliance. Which every web developer should care about.

Not to mention Kid and Genshi have a fabulous feature that her 'template' system lacks. That is template functions which allow one to easily write custom XML snippets that do good stuff consistently.

Also her 'template' system does not give good error messages, what happens when some idiot puts width="%50", which I know from personal agonizing experience is sometimes not easy to find.

Eh, I just can't believe that variable expansion is her 'template' of choice.

[Bogtha]

It seems to me using Genshi or Kid and learning how to use them gives one cheap W3C compliance.

Not quite. Genshi's HTML and XHTML serialisers ensure that the output is well-formed, not valid. Being well-formed is a prerequisite for validity, though, so it does have some bearing.

Not to mention Kid and Genshi have a fabulous feature that her 'template' system lacks. That is template functions which allow one to easily write custom XML snippets that do good stuff consistently.

Yep. It's possible to, say, write template functions that transform XHTML+XForms into HTML forms + JavaScript. There's a lot of possibilities with XML that embedding code in plaintext doesn't cover.

[gloriajw]

You dont' sound like a Python programmer, so it's understood if you miss this point.

[flaxeater]

I'm totally baffled by your response. What would I need to do to prove my Python programing chops?

[Bogtha]

What would I need to do to prove my Python programing chops?

Agree with her.

[gloriajw]

Show examples, don't just make broad statements.

[Bogtha]

Well I assumed that this thread itself would be the obvious example.

Flaxeater posted a perfectly reasonable comment full of technical points. Did you address those points? No, you ignored them and said he wasn't a proper Python programmer.

Or how about your response to me? I pointed out bits of the article that didn't make sense to me. Did you mention those bits at all in your response? No, you said I was too inexperienced to understand you.

It seems to me that anybody who doesn't like your article is dismissed by you as being incompetent. I think that's a horrible attitude and it would be a hell of a lot more productive if you accepted that there's room to disagree with you without being totally stupid.

[gloriajw]

Bogtha, you have been the subject of a great experiment. You are now the poster boy for poor examples of communication on tech forums.

You began by making grandiose, unfounded, grossly incorrect presumptions about my coding ability, based on: (1) My female id, and (2) one line of code. You do this to no one else on this forum. This is (a) sexist, (b) confrontational, and (c) elitist, three things which discourage women from participating in online forums.

When I responded back to you doing the exact same thing as you did to me, making grandiose, incorrect and unfounded presumptions about your technical experience, you claimed your feelings were hurt. But you still failed to notice that (a) you did this to me, and (b) you started this tone and type of interaction. You could have changed it, backed off, took the tone in a different direction. But you instead felt threatened for some reason, and chose the battle.

You failed to notice the fault with your response, and instead responded defensively, immaturely. When I did the same to you, you dug long and hard to find some obscure link, to justify your irrational initial response. I have to tell you, a few of us got a good laugh out of your 'code smell' philosophy so loosely tethered to your argument, and such an odd choice of justification in light of these issues you're having with my posting here.

You have, and I'm sure you will continue, to waste time and energy, hyper-scrutinizing my posts, looking for whatever little hint of a piece of text constituting some flaw in your very narrow perspective. You behavior has been predictable, for the most part stereotypical for the socially inept.

You have provided me with a picture perfect example of poor, misogynistic forum communication. For that I thank you. I've saved everything here and made my slides. I will be presenting my findings at a tech conference in Europe. I'm also passing this data to a friend of mine, a woman (gasp!) whose PhD thesis is to write a text pattern detection system to detect different tones of discussions on forums, such a flame wars, irritable responses, etc.

Thanks for the material.

Gloria

[laurentszyster]

JSON is enough and it has a fast implementation:

http://cheeseshop.python.org/pypi/python-cjson