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I teach undergraduate statistics, and am interested in administering personalized online assignments. I have already solved one portion of the puzzle, the generation of multiple version of a question using latex/markdown + knitr/sweave, using seeds.
I am now interested in developing a web-based system, that would use the various versions generated, and administer a different one for each student, online. I have looked into several sites related to forms (google docs, wufoo, formsite etc.), but none of them allow programmatic creation of questionnaires.
I am tagging this with R since that is the language I am most familiar with, and is key to solving the first part of the problem. I know that there are several web-based frameworks for R, and was wondering whether any of them are suitable for this job.
I am not averse to solutions in other languages like Ruby, Python etc. But the key consideration is the ability to programatically deliver online assignments. I am aware of tools like WebWork, but they require the use of Perl and the interfaces are usually quite clunky.
Feel free to add tags to the post, if you think I have missed a framework that would be more suitable.
EDIT. Let me make it clear by giving an example. Currently, if I want to administer an assignment online, I could simply create a Google Form, send the link to my students, and collect all responses in a spreadsheet, and automatically grade it. This works, if I just have one version of the assignment.
My questions is, if I want to administer a different version of the assignment for each student, and collect their responses, how can I do that?
The way you have worded your question it's not really clear why you have to mark the students' work online. Especially since you say that you generate assignments using sweave. If you use R to generate the (randomised) questions, then you really have to use R to mark them (or output the data set).
For my courses, I use a couple of strategies.
For the end of year exam (~500 students), each student gets a unique data set. The students log on to a simple web-site (we use blackboard since the University already has it set up). All students answer the same questions, but use their own unique data set. For example, "What is the mean". The answers are marked offline using an R script.
In my introductory R course, students upload their R functions and I run and mark them off line. I use sweave to generate a unique pdf for each student. Their pdf shows where they lost marks. For example, they didn't use the correct named arguments.
Coupling a simple web-form with marking offline gives you a lot of flexibility and is fairly straightforward.
I found one possible solution that might work using the RGoogleDocs package. I am posting this as an answer only because it is long. I am still interested in better approaches, and hence will keep the question open.
Here is the gist of the idea, which is still untested.
Create multiple versions of each assignment using knitr/Sweave.
Upload them to GoogleDocs using uploadDoc.
Share one document per student using setAccess which modifies access controls.
Create a common Google Form to capture final answers for each student.
The advantage I see is two-fold. One, since all final answers get captured on a spreadsheet, I can access them with R and grade them automatically. Two, since I have access to all the completed assignments on Google Docs, I can skim through them and provide individual comments as required (or let some of my TAs do it).
I will provide an update, if I manage to get this working, and maybe even create an R package if it would be useful for others.
I know that this was asked a long time ago, but I think that today the best solution is the package exams plus Moodle.
The package exams can now generate XML Moodle questions that can be upload to Moodle platform as the students can solve the exercices on-line.
This is an example of a question made with exams package and uploaded to Moodle.
i just stumbled upon the ?exams package in R: Link to the CRAN site. could this be something for you?
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So, I’m learning python and discord.py, and out of a bot with 500 lines of code, I only asked help with one item. The rest, I’ve been researching myself and trial and error. I’m currently at a cross roads, and would like some advice which route to take. I’m not looking to ask how, I’ll figure that on my own ( hopefully ).
So, I have a bot running on my Windows PC, only running on a single server, which is my own. The bot returns an embedded message with a list of inactive users, which is based on a series of roles. After a few nested IF statements, it adds the field with person.mention. Then posts the list to a specific channel, mentioning them all.
As per rules, they have 48 hours to improve their activity, which will modify their roles.
So, while the first command works like a charm, I’m looking to create a second command that goes through the list of users from the previous “audit” ( typically about 15-30 people ) check them to see if their activity has improved ( if set of roles exist ) and report back in a staff channel “Members out of compliance, and subject to removal:” then the list of saved users wiped for the next audit. ( twice a month )
To do this, I need to research how, but for the sake of saving me time, I’m asking which route should I investigate and why? Text File? DB? Or JSON?
I appreciate everyone’s input.
I'd normally suggest using a small database (like sqlite) for small bots, but if you're new to python you shouldn't learn SQL. I guess using a JSON file works, though using them as a database is not a great idea, it's mostly used as a config file. A few downsides of using JSON files are:
It's a file-based data storage, which makes it vulnerable to race conditions.
You'll need to implement your own synchronization primitives to avoid corrupting data.
If you're not careful, you could accidentally wipe your entire JSON file.
Another alternative to JSON files are yaml or toml files, but the downsides are the same.
Using databases:
If you want to learn SQL (there are good, free, easy to follow sources out there like sqlbolt) the advantages are:
Databases organize your data into tables, and are fast at inserting, retrieving, and removing records.
You can impose uniqueness constraints to ensure against duplication.
The Python libraries enforce synchronization for you.
The query language is intuitive, you can get running with simple queries in just a few hours!
MongoDB is an excellent choice for a database, I haven't personally used it but it's a good non-relational database (doesn't use SQL).
PS: Don't even think about using txt files as a database, that's a bad, bad, bad idea.
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For a class, I would like to automatically evaluate (parts) of the coding assignments of students. The setup I had in mind is something like:
Students get a class skeleton, which they have to fill in.
Students ``upload'' this class definition to a server (or via webinterface)
The server runs a script an test on specific functions, eg class.sigmoid(x), and checks if the output of the function is correct and might give suggestions.
This setup brings a whole lot of problems, since you're evaluating untrusted code. However, it would be extremely useful, for many of my classes, so I'm willing to spend some time in thinking it trough. I remember Coursera had something similar for matlab/octace assignments, but I can't get the details of that.
I've looked at many online python interfaces (eg, codecademy.com, ideone.com, c9.io); while they seem perfect to learn and or share code, with online evaluation. I do miss the option, that the evaluation script is "hidden" from the students (ie the evaluation script should contain a correct reference implementation to compare output on random generated data). Moreover, the course I give requires some data (eg images) and packages (sklearn / numpy), which is not always available.
Specifically, my questions are
Do I miss an online environment which actually offers such a functionality. (that would be easiest)
To set this up myself, I was thinking to host it at (eg) amazon cloud (so no problem with infrastructure at University), but are there any python practices you could recommend on sandboxing the evaluation?
Thanks in advance for any suggestions!
Pity to hear that the question is not suitable for StackOverflow. Thanks to the people (partially) answering the question.
After some more feedback via other channels, I think my approach will become as follows:
Student gets skeleton and fills it in
Student also has the evaluation script.
In the script, some connections with a server are made to
login
obtain some random data
check if the output of the students code is numerically identical to what the server expects.
In this way the students code is evaluated locally, but only output is send to the server. This limits the kind of evaluations possible, but still allows for kind of automatic evaluation of code.
Sandboxing Python in general is impossible. You can try to prevent dangerous operations, which will mean significantly limiting what the student code can do. But that will likely leave open attack vectors anyway. A better option is to use OS-level sandboxing to isolate the Python process. The CodeJail library uses AppArmor to provide a safe Python eval, for example.
As an example of the difficulty of sandboxing Python, see Eval really is dangerous, or consider this input to your sandbox: 9**9**99, which will attempt to compute an integer on the order of a googolplex, consuming all of your RAM after a long time.
This is currently a very active field in programming languages research.
I know of these two different approaches that look at the problem:
- http://arxiv.org/pdf/1409.0166.pdf
- http://research.microsoft.com/en-us/um/people/sumitg/pubs/cacm14.pdf (this is actually only one of very many papers by Sumit and his group)
You may want to look at these things to find something that could help with your problem (and edit this answer to make it more useful).
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First I want to clearify that I mean by reverse engineering something like "decompiling" and getting back the original source code or something similiar.
Yesterday I read a question about someone who wanted to protect his python code from "getting stolen" in other words: he didn't like that someone can read his python code.
The interesting thing I read was that someone said that the only reliable way to "protect" his code from getting reverse engineered is by using a Webservice.
So I could actually only write some GUIs in Python, PHP, whatever and do the "very secret code" I want to protect via a Webservice. (Basically sending variables to the host and getting results back).
Is it really impossible to reverse engineer a Webservice (via code and without hacking into the Server)? Will this be the future of modern commercial applications? The cloud-hype is already here. So I wouldn't wonder.
I'm very sorry if this topic was already discussed, but I couldn't find any resources about this.
EDIT: The whole idea reminds me of AJAX. The code is executed on the server and the content is sent to the client and "prettified". The client himself doesnt see what php-code or other technology is behind.
Wow, this is awesome! I've never thought it this way, but you could create a program that crawls an api, and returns as an output a django/tastypie software that mimics everything the api does.
By calling the service, and reading what it says, you can parse it, and begin to see the relationships between objects inside the api. Having this, you can create the models, and tastypie takes it from this point.
The awesome thing about this, is that normal people (or at least not backend developers) could create an api just by describing what they want to be as an output. I've seen many android/iphone developers creating a bunch of static xml or json, so they can call their service, and start the frontend development. Well what if that was enough? Take some xml/json files as input, get a backend as an output.
Yes,
All they could do is treat your web service as a black box, query the WSDL for all the parameters it accepts and the data that it returns.
They could then submit different variables and see what different results are. The "code" could not be seen or stolen (with proper security) but the inputs and outputs could be duplicated.
If you want to secure your "very secret code" a web service is a great way to protect the actual code.
-sb
It depends on what you mean by reverse engineering: by repeatedly sending input and analyzing the output the behaviour of your code can still be seen. I wouldn't have your code but I can still see what the system does. This means I could build a similar system that does the same thing, given the same input.
It would be hard to catch exceptional cases (such as output that is different on one day of the year only) but the common behaviour can certainly be copied. It is similar to analyzing the protocol of an instant messaging client: you may not have the original code but you can still build a copy.
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I've written a few little things in python, and I am ramping up to build something a little more challenging.
The last project I made basically ingested some text files, did some regex over each file and structured the data in an useful way so I could investigate some data I have.
I found it quite tough near the end to remember what section operated on what part of the text, especially as the code grew as I 'fixed' things along the way.
In my head, I imagine my code to be a series of small interconnected modules - descrete .py files that I can leave to one side knowing what they do, and how they interoperate.
The colleague that showed me how to def functions basically meant that I ended up with one really long piece of code that I found really hard to navigate and troubleshoot.
(1) Is this the right way? or is there an easier way of making modules that pass variables between them, I think i would find this better, as I could visualise the flow better (mainly becuase its how I was used to working in MATLAB a few years ago I guess)
(2) Can you use this method to plan out the various layers of functions before hand to give you a 'map' to write towards?
(3) is there any easy to access tutorials for this kind of stuff? I often find the tutorials suddenly jump way over my head....
Thanks.
(1) It is possible to write a fine programme in a single .py file
(2) In any style of programming, it is always (apart from special, hardware-driven cases) best to break your code up into short functions (or methods) that accomplish a discrete task.
(3) Experienced programmers will frequent write their code one way, discover a problem, either write more code, or different code, and consider whether any of their existing code can be broken out into a separate function.
A sign that you need to do this is when you are sequentially assigning to variables to pass data down your function. Never copy-paste your code to another place, even with changes, unless it be to break it out as a function, and replace the original code with a call to that function.
(4) In many cases, it can be useful to organise your code into classes and objects, even when it is not technologically necessary to do so. It can help you see that you have defined a complete set of operations (or not) necessary on some collection of data.
(5) Programming is actually quite hard. Even among those who have a talent for it, it takes a while to be comfortable. As an illustration, when I was doing my master's degree, I and my (fairly talented) friends all felt only in our final year that we had begun to achieve a degree of facility and competence (and these are all people who had been programming since at least their teenage years).
The important thing is to keep learning and improving, rather than repeating the same one or two years of experience over and over.
(6) To that end, read books and articles. Try new things. Think.
Others have suggested studying other experienced programmers' code from open source projects, etc. and from tutorials and textbooks, which is sound advice. Sometimes a similar example is all you need to set you on the right path.
I also suggest to use your own frustration and experience as feedback to help yourself improve. Whenever you find yourself thinking any of the following:
It feels like I'm writing the same code over and over again with only small changes
I wrote this code myself, but I had to study it for a long time to re-learn how it works
Each time I go back and add something to this code it takes me longer to get it working again
There's a bug in this code somewhere, but I haven't a clue where
Surely somebody somewhere has solved this problem already
Why is this taking me so long to get done?
That means you have room for improvement in your technique. A lot of the difference between an expert and beginning programmer is the ability to do the following:
Don't Repeat Yourself (DRY): Instead of copy-pasting code, or writing the same code over and over with variations, write a single common routine with one or more parameters that can do all of those things. Then call that routine in multiple places.
Keep It Simple (KIS): Break up your code into simple well-defined behaviors/routines that make sense on their own, organized into classes/modules/packages, so that each part of the overall program is easy to understand and maintain. Write informative and concise comments, and document the calls even if you don't intend to publish them.
Divide & Conquer Testing: Thoroughly test each individual class, function, etc. by itself (preferably with a unit-testing framework) as you develop it, rather than only testing the entire application.
Don't Re-invent the Wheel: Use open source frameworks or other tools where possible to solve problems that are general and not specific to your application. In all but the most trivial cases, there is a risk that you do not fully understand the problem and your home-grown solution may be lacking in an important way.
Estimate Honestly: Study your own previous efforts to learn how long it takes you to do certain things. Try to work faster next time, but don't assume you will. Measure yourself and use your own experience to estimate future effort. Set expectations and bargain with scope.
It's hard to know even where to begin answering your question without a snippet of your code for reference. You might want to post your code to a free public site such as http://www.bitbucket.org/ or http://www.github.org/ and then include some specific questions about small snippets of code with links back to your repository. This allows respondents here to look at the code and comment on it. (Both of these options even include color syntax highlighting, and interested correspondent can even pull the code down, make changes and push up a patch or create their own branch of your code and send you a "pull" request so you can look at the differences and pull selected changesets back into your branch).
More generally there are a number of approaches to program design. You seem to be trying to re-invent a very old methodology which is referred to as "functional decomposition" --- look at the overall task at hand as a function (digest text files) and consider how that breaks down (decomposes) into smaller functions (ingest input files, parse them, prepare results, output those) and then breaking those down further until you have units which are small enough to be coded easily in your programming environment (Python).
Modern approaches (and tools) tend to use object oriented design methodologies. You might try reading: http://www.itmaybeahack.com/homepage/books/oodesign/build-python/html/index.html
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I am looking for tutorials and/or examples of certain components of a social network web app that may include Python code examples of:
user account auto-gen function(database)
friend/follow function (Twitter/Facebook style)
messaging/reply function (Twitter style)
live chat function (Facebook style)
blog function
public forums (like Get Satisfaction or Stack Overflow)
profile page template auto-gen function
I just want to start getting my head around how Python can be used to make these features. I am not looking for a solution like Pinax since it is built upon Django and I will be ultimately using Pylons or just straight up Python.
So you're not interested in a fixed solution but want to program it yourself, do I get that correctly? If not: Go with a fixed solution. This will be a lot of programming effort, and whatever you want to do afterwards, doing it in another framework than you intended will be a much smaller problem.
But if you're actually interested in the programming experience, and you haven't found any tutorials googling for, say "messaging python tutorial", then that's because these are large-scale projects,- if you describe a project of this size, you're so many miles above actual lines of code that the concrete programming language almost doesn't matter (or at least you don't get stuck with the details). So you need to break these things down into smaller components.
For example, the friend/follow function: How to insert stuff into a table with a user id, how to keep a table of follow-relations, how to query for a user all texts from people she's following (of course there's also some infrastructural issues if you hit >100.000 people, but you get the idea ;). Then you can ask yourself, which is the part of this which I don't know how to do in Python? If your problem, on the other hand, is breaking down the problems into these subproblems, you need to start looking for help on that, but that's probably not language specific (so you might just want to start googling for "architecture friend feed" or whatever). Also, you could ask that here (beware, each bullet point makes for a huge question in itself ;). Finally, you could get into the Pinax code (don't know it but I assume it's open source) and see how they're doing it. You could try porting some of their stuff to Pylons, for example, so you don't have to reinvent their wheel, learn how they do it, end up in the framework you wanted and maybe even create something reusable by others.
sorry for tl;dr, that's because I don't have a concrete URL to point you to!