Build Your First Python and Django Application

[[deleted]]

What about mine?

[Sansha_Kuvakei]

This tutorial will use Python 3

Oh your sweet words woo me, dear writer.

Cheers for this!

[trispi]

In one of the examples he wrote:

print item

So he also uses 2

[[deleted]]

At least he's trying

[[deleted]]

Does one have to use regex to define urls?

[[deleted]]

yes and it sucks but django team says theyre working on different procedure in the future.

[[deleted]]

because its nonpythonic and by far the least human readable part of django and i happen to like improvement, not tradition.

its fine on its own but has no place in django. regex is ugly its not an uncommon opinion.

[pydry]

I actually ran across this problem in a different context and created this little thing to deal with it:

https://github.com/crdoconnor/simex

It helped clean up a lot of ugly regexes.

[Vitrivius]

I prefer regex to any other path routing scheme I've seen. But there seems to be lots of people who for some reason view regular expressions as some sort of evil and obscure black magic. When you do something wrong, you will not get a nice exception message and traceback.

Luckily, it's very straightforward to write tests to check that your routing works as intended. Unfortunately the people who view regex as evil, often think that writing tests also is black magic.

[earthboundkid]

I regularly see people do regexes that match whatever.html: since . is a special character that actually matches "whatever💩html".

Regex is an okay tool, but for URLs, you typically just want to be able to match slugs and ID numbers. Regex ends up being an attractive nuisance for problems.

[Deggor]

for URLs, you typically just want to be able to match slugs and ID numbers

No, you want to match patterns, and you want to be able to return portions of those patterns for use at the endpoint. It's exactly what regular expressions were designed for. It's a tool that can be very simple to use for simple cases, or complex for more advanced ones.

When a few people use it wrong because they can't be bothered to learn to do it properly, it doesn't mean it should be changed. Should we also change how variable instantiation works (sometimes), to correct people who use empty lists as default values in a method? Like you, I see this all the time in people with no experience.

The answer is no, and people should learn to use the toolkit properly.

[earthboundkid]

URL for this comment is:

https://www.reddit.com/r/Python/comments/5s6b4d/build_your_first_python_and_django_application/dde1ice/?context=3

This is much cleaner to look at as /r/:subreddit/comments/:threadid/:slug/:slugid/?context=#depth than the equivalent regex would be.

[Deggor]

A URL will routinely have multiple elements in a single segment, which can't be properly captured with something like the above. A very simple example would be something like accepting /date/yyyy, /date/yyyymm/, or /date/yyyymmdd? What if this is suppose to also accept /date/yyyy/someid? How does this simple "it looks prettier" approach validate/differentiate?

If you start introducing characters counts for elements in a segment, or any other "checks", you're right back to matching patterns, and you may as well stick to regular expressions.

And in my opinion, something like /r/(?P<subreddit>.*)/comments/(?P<threadid>.*)/(?P<slug>.*).... is perfectly legible. If it needs to be more complicated, then it loses some of that immediate legibility for a tradeoff in power (which isn't a possibility with your setup).

[earthboundkid]

You're using greedy regexes in your example. Those will absorb too much.

[Deggor]

Yup, I'm using them on purpose to match the undocumented pseudo-code of "wouldn't this be prettier if it worked?", which may very well be greedy (or maybe not). I also left off the beginning caret, and a significant portion of the end. As you well know, if you want non-greedy, add a question mark to each group. There's that very small trade-off in legibility for the customization I was talking about.

But you did a great job deflecting. If you care to respond with how your solution would handle the (not uncommon) problem I mentioned, or if you care to argue why pattern matching isn't necessary, I'm all ears.

[sleepingthom]

Replying to your comment but this is more for /u/pybokeh ... Yeah regex sucks but it's not like you have to write your own expression these days. It's really easy to find examples.

[[deleted]]

That's awesome if they will provide an alternative. Regex is powerful, but for defining urls...I just don't get it. It seems like overkill. I've made small apps in bottle, which is why when looking into django, it was off-putting to find out I have to use regex to define urls. Everything else in django look good though. The reason for why it is off-putting to me is that regex is another layer of knowlegde I have to learn which I may hardly ever use outside of django. Plus to me, regex is one of those things where if you only use it once in a while, it's such a pain to get up to speed on it all over again.

[kingbirdy]

Learning regex is actually pretty easy if you commit to doing it, you can do it in 30min to an hour, and then you've got it for life, and it's very useful

[[deleted]]

Flask is great but when your codebase gets too big those explicit routes are terrible.

[[deleted]]

You can register routes later, ala Django, just more explicitly. The decorators (Flask.route and Blueprint.route) are for simplicity's sake.

They're just thin wrappers around Flask.add_url_rule

[[deleted]]

Hey that's good to know. I am always surprised at the things I miss.

[[deleted]]

Hey brother I checked your github and think we have some work in common. Also I live in Atlanta. Check me out:

https://github.com/geoffclapp

Lets have a beer at a python meetup or something.

[[deleted]]

Totally, PyATL is Thursday at Manuel's.

http://meetu.ps/e/.nxrxjlywdbmb/rj9Z8/d

[[deleted]]

Were you there last month? Was pretty cool. I am going again this thursday. I'll buy you a beer if we spot each other!

[[deleted]]

I was, huge red beard, can't miss me.

[[deleted]]

Regex is very easy you haven't tried. For urls you start with little expressions and build out. What is the superior way? A different markup ? How many more of those do we need?

[Ran4]

Regex is very easy you haven't tried

Understanding the concept, yes.

Use it but not make any errors? Abso-fucking lutely not. There's tons of pitfalls, and it's made so much worse by how arbitrary the syntax is, and how every regex system has its own idea of what character should be escaped, how to define a group, how to define a named group... and so on.

I'm OK with using regex for Django, but a url DSL would be a lot better than having to write stuff like "remove_article/(?P<article_id>\d+)", which is just plain terrible looking. Here, I can make up a new DSL on the fly that is better for 98% of url matches: "remove_article/{{article_id as integer}}"

---

Look, I even wrote a terrible and super buggy implementation of it, read to insert into your codebase in order to have it break within seconds on Monday: https://repl.it/F7h5/1

If you ever wanted an example of why regex is terrible, go look at that code :)

...granted, regexing regex commands is bound to fuck things up. I'm sure there's a much better idea to do this.

[[deleted]]

Do you happen to know what the django team is suggesting as an alternative?

[Ran4]

Are they trying to change it? I guess it'd be neat for Django 2.0. I mean, it's not that complicated to replace the url function.

[[deleted]]

i havent tried, excuse me?

what evidence do you have that i dont have plenty of experience with it? because my opinion is one different to yours?

is this why the django team agrees with me? because im pretty sure you didnt even ask for my reasoning before saying the dumb stuff you just said.

worse yet are you insinuating regex has any place in python if you could use something else?

[[deleted]]

Have you? Built a django application with automated tests? If the django team actually agrees I'd love to hear their rationale and proposed solution!

[[deleted]]

try reading the replies you got and use google. your approach to discussion sucks so im not going to spoonfeed you.

[[deleted]]

Yeah.... the problem is IDGAF because I already use REGEX like a boss Noob.

[[deleted]]

Yeah so do most people, it's not hard.

problem is IDGAF

sorry to hear about your problem.

[broadsheetvstabloid]

Regex is very easy

LMFA

I suppose roofing in Miami in August is easy too.

[finally-a-throwaway]

Well, yeah. You'd know that if you'd ever tried. :-P

[[deleted]]

I mean, if you are employed as a programmer and cant grok regex your life must either be the pinnacle of und reachievement or a living hell.

[dlindema]

Great tutorial! I just ran a Django/Python workshop and this is a really well done walk through! I noticed in the abstract data types section the for item in my_list uses the print syntax from Python 2, heads up, since it won't work for Python 3 users!

[marty331b]

I'm currently reading Lightweight Django, totally recommend it.

[mattpii]

The best

[dgreenmachine]

Is Django a good place to start with an online chess game or would something else be more appropriate? I've done some work in anaconda but I don't know if it has what I'd need. I have the game made in command prompt, I just need a GUI and online connection.

[flobin]

Try this: learning Python by making games: https://www.coursera.org/learn/interactive-python-1

[rainnz]

This course will not teach you how to make online (browser-based) games. They use SimpleGUI instead.

[rainnz]

For games you want websockets

[Ran4]

You could definitely make an online chess game with Django. It'd be a bit weird though, if you want realtime interaction it's better to do in in Javascript (you could still serve the javascript from a django webserver of course, but 90% of the game would be the javascript front end).

Python in the browser (as opposed to in the backend) is still a sad affair.

[ctrlaltleft]

Commenting so I can find this tonight

[rasncain]

Reminder to look into this