SparkEd | presenting educational and training content | Learning library
kandi X-RAY | SparkEd Summary
kandi X-RAY | SparkEd Summary
Software for organizing and presenting educational and training content for delivery on most platforms. SparkEd was deployed on a server and it loaded more than 1,500 resources. It worked very well in an office setting and was tested with 20 hosts. We plan to deploy the system in a school with more than 600 students. To get started check out our wiki. Check here for the online documentation how to use this project and a small demo here accessible on big screens. Note: We only support Node^10.
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QUESTION
As stated in the title, my goal is to find a regex that matches a word if and only if it contains a substring of exactly two consecutive characters which is not surrounded by that same character.
Test casesHelo-->falseprogramming-->truebelllike-->false(since there are threels)shellless-->true(even though there are threels, this input should match because of the twoss
The regex [a-zA-Z]*([a-zA-Z])\1[a-zA-Z]* matches a word with at least two consequtive characters, but belllike would still match because there is no upper limit on consecutive characters.
I also tried to use negative lookaheads and lookbehinds. For one letter, this may look like this:
[a-zA-Z]*(?
This regex fulfills all requirements for the letter a but neither I nor the people I asked could generalize it to using capture groups and thus working for any letter (copy-pasting this statement 26 times - once for each letter - and combining them with OR is not the solution I am looking for, even though it would probably work).
What I'm looking for
A solution for the described problem would be great, of course. If it cannot be done with regex, I would be equally as happy about an explanation on why that is not possible.
Background
This task was part of an assignment I had to do for uni. In a dialogue, the prof later stated that they didn't actually want to ask that question and were fine with accepting character sequences of three or more identical characters. However, the struggle of trying to find a solution for this problem sparked my interest on whether this is actually possible with regex and if so, how it could be done.
Regex flavor to use
Even though the initial task should be done in the Java 8+ regex flavour, I would be fine with a solution in any regex flavor that solves the described problem.
...ANSWER
Answered 2021-May-08 at 11:51You can try:
QUESTION
Working with Pyspark using the withColumn() command in order to do some basic transformation on the dataframe, namely, to update the value of a column. Looking for some debug assistance while I also strudy the problem.
Pyspark is issuing an AnalysisException & Py4JJavaError on the usage of the pyspark.withColumn command.
_c49='EVENT_NARRATIVE' is the withColumn('EVENT_NARRATIVE')... reference data elements inside the spark df (dataframe).
...ANSWER
Answered 2021-Mar-21 at 06:53The column names are in the form of _c followed by a number, because presumbaly you did not specify header=True while reading the input file. You can do
QUESTION
I am a Python novice who took one course on the subject last semester, which really sparked my interest. Right now I am trying to figure out some more "advanced" concepts on my own, the first one being recursion. I have been trying an exercise from a handbook I'm following, which basically boils down to: "recursively find a n-digit code consisting out of unique digits between 0 and 9."
This builds upon the previous exercise, which does not have the requirement of unique digits. I solved that one as shown below.
...ANSWER
Answered 2021-Feb-13 at 15:23Answering Question1: this is an ideal use case for exceptions.
The problem with 'return' is that your recursion has piled up many calls to crack_code, and return only brings you back one level, to where you last called crack_code. Since that's inside a 'for' loop, it'll continue looping.
To break out of all the crack_code calls, define a new exception class:
QUESTION
I am trying to understand all the low-level stuff Compilers / Interpreters / the Kernel do for you (because I'm yet another person who thinks they could design a language that's better than most others)
One of the many things that sparked my curiosity is Async-Await. I've checked the under-the-hood implementation for a couple languages, including C# (the compiler generates the state machine from sugar code) and Rust (where the state machine has to be implemented manually from the Future trait), and they all implement Async-Await using state machines. I've not found anything useful by googling ("async copy stack frame" and variations) or in the "Similar questions" section.
To me, this method seems rather complicated and overhead-heavy;
Could you not implement Async-Await by simply memcopying the stack frames of async calls to/from heap?
I'm aware that it is architecturally impossible for some languages (I thank the CLR can't do it, so C# can't either).
Am I missing something that makes this logically impossible? I would expect less complicated code and a performance boost from doing it that way, am I mistaken? I suppose when you have a deep stack hierarchy after a async call (eg. a recursive async function) the amount of data you would have to memcopy is rather large, but there are probably ways to work around that.
If this is possible, then why isn't it done anywhere?
...ANSWER
Answered 2020-Aug-23 at 18:38I would first like to begin by saying that this answer is only meant to serve as a starting point to go in the actual direction of your exploration. This includes various pointers and building up on the work of various other authors
I've checked the under-the-hood implementation for a couple languages, including C# (the compiler generates the state machine from sugar code) and Rust (where the state machine has to be implemented manually from the Future trait), and they all implement Async-Await using state machines
You understood correctly that the Async/Await implementation for C# and Rust use state machines. Let us understand now as to why are those implementations chosen.
To put the general structure of stack frames in very simple terms, whatever we put inside a stack frame are temporary allocations which are not going to outlive the method which resulted in the addition of that stack frame (including, but not limited to local variables). It also contains the information of the continuation, ie. the address of the code that needs to be executed next (in other words, the control has to return to), within the context of the recently called method. If this is a case of synchronous execution, the methods are executed one after the other. In other words, the caller method is suspended until the called method finishes execution. This, from a stack perspective fits in intuitively. If we are done with the execution of a called method, the control is returned to the caller and the stack frame can be popped off. It is also cheap and efficient from a perspective of the hardware that is running this code as well (hardware is optimised for programming with stacks).
In the case of asynchronous code, the continuation of a method might have to trigger several other methods that might get called from within the continuation of callers. Take a look at this answer, where Eric Lippert outlines the entirety of how the stack works for an asynchronous flow. The problem with asynchronous flow is that, the method calls do not exactly form a stack and trying to handle them like pure stacks may get extremely complicated. As Eric says in the answer, that is why C# uses graph of heap-allocated tasks and delegates that represents a workflow.
However, if you consider languages like Go, the asynchrony is handled in a different way altogether. We have something called Goroutines and here is no need for await statements in Go. Each of these Goroutines are started on their own threads that are lightweight (each of them have their own stacks, which defaults to 8KB in size) and the synchronization between each of them is achieved through communication through channels. These lightweight threads are capable of waiting asynchronously for any read operation to be performed on the channel and suspend themselves. The earlier implementation in Go is done using the SplitStacks technique. This implementation had its own problems as listed out here and replaced by Contigious Stacks. The article also talks about the newer implementation.
One important thing to note here is that it is not just the complexity involved in handling the continuation between the tasks that contribute to the approach chosen to implement Async/Await, there are other factors like Garbage Collection that play a role. GC process should be as performant as possible. If we move stacks around, GC becomes inefficient because accessing an object then would require thread synchronization.
Could you not implement Async-Await by simply memcopying the stack frames of async calls to/from heap?
In short, you can. As this answer states here, Chicken Scheme uses a something similar to what you are exploring. It begins by allocating everything on the stack and move the stack values to heap when it becomes too large for the GC activities (Chicken Scheme uses Generational GC). However, there are certain caveats with this kind of implementation. Take a look at this FAQ of Chicken Scheme. There is also lot of academic research in this area (linked in the answer referred to in the beginning of the paragraph, which I shall summarise under further readings) that you may want to look at.
Further Readingcall-with-current-continuation
This answer (contains few links to academic research in this area)
TLDRThe decision of which approach to be taken is subjective to factors that affect the overall usability and performance of the language. State Machines are not the only way to implement the Async/Await functionality as done in C# and Rust. Few languages like Go implement a Contigious Stack approach coordinated over channels for asynchronous operations. Chicken Scheme allocates everything on the stack and moves the recent stack value to heap in case it becomes heavy for its GC algorithm's performance. Moving stacks around has its own set of implications that affect garbage collection negatively. Going through the research done in this space will help you understand the advancements and rationale behind each of the approaches. At the same time, you should also give a thought to how you are planning on designing/implementing the other parts of your language for it be anywhere close to be usable in terms of performance and overall usability.
PS: Given the length of this answer, will be happy to correct any inconsistencies that may have crept in.
QUESTION
I am trying to normalize (perhaps not the precise term) a nested JSON object in PySpark. The actual data I care about is under articles. The schema is:
ANSWER
Answered 2020-Jun-15 at 23:37This should work. Let me know if you have any questions
QUESTION
I'm trying (and failing) to compile a fortran module (specifically igrf12.f from the BGS) using f2py and Python 3.6 on Windows 10. Python was installed using Anaconda 4.4.10.
My setup:
- Python 3.6.3 |Anaconda custom (64-bit)| (default, Oct 15 2017, 03:27:45) [MSC v.1900 64 bit (AMD64)] on win32
- Windows 10 Enterprise (version 1703)
- NumPy 1.14.0
I followed f2py directions from the SciPy documentation and a very helpful guide from Dr.Michael Hirsch. Dr.Hirsch has created the pyigrf12 module, but installation through pip failed for me, which is what initially sparked my interest in f2py.
I will outline a few of the methods I am using. Regardless of the method, I always begin by creating a *.pyf signature file using f2py igrf12.f -m pyigrf12 -h igrf12.pyf and adding intent(in/out) attributes appropriately.
- Method 1: Use C:\MinGW and
--compiler=mingw32 - Method 2: Use C:\MinGW and
--compiler=msvc - Method 3: use anaconda version of mingw and
--compiler=mingw32 - Method 4: use anaconda version of mingw and
--compiler=msvc
Method 1:
For background, I have MinGW at C:\MinGW and I have added C:\MinGW\bin to my user Path. Unfortunately, I did not install this version of MinGW (I inherited this computer from a colleague), so I do not know where it was sourced. The gcc --version and gfortran --version is 5.3.0.
I run f2py -c igrf12.pyf igrf12.f --compiler=mingw32. This fails with this error message:
ANSWER
Answered 2020-May-07 at 19:11Finally got this working.
Short version:
Make sure you use 64-bit compilers (triple check the build for mingw-w64) for 64-bit Python. Not as obvious as it sounds to an f2py newb on Windows.
Long version:
I uninstalled my existing copy of MinGW (I suspect it was a 32 bit version) and instead downloaded a specific 64-bit build of mingw-w64 7.2.0 from sourceforge, specifically x86_64-7.2.0-release-posix-seh-rt_v5-rev1.7z. This stackoverflow question was useful.
I unzipped and copied the "mingw64" folder into my C: drive (C:\mingw64). I added C:\mingw64\bin to my user Path.
I uninstalled the anaconda version of MinGW with conda uninstall mingw. Note, this is only necessary if you've previously installed MinGW using conda.
Upon running f2py -c igrf12.pyf igrf12.f --compiler=mingw32 (in same directory as igrf12.pyf, see Scipy Documentation for how to generate *.pyf file), pyigrf12.cp36-win_amd64.pyd is created without any errors. I can finally import pyigrf12 successfully and access the underlying Fortran subroutines (e.g. igrf12syn).
Note, I can also run f2py -c igrf12.pyf igrf12.f --compiler=msvc successfully, but then I have to manually copy and paste the libigrf12....gfortran-win_amd64.dll (generated in .\UNKNOWN\.libs\) into the same directory as pyigrf12.cp36-win_amd64.pyd to avoid ImportError: DLL load failed: The specified module could not be found. mentioned in Method 2 of my question.
Just to re-iterate: Make sure C:\mingw64\bin is added to your path!
By the way, f2py was painless for me on macOS Sierra and Ubuntu. If the above still doesn't work for you, I recommend trying on Linux, macOS or Windows Subsystem for Linux.
QUESTION
This question sparked when I was setting the base case of the following code:
...ANSWER
Answered 2020-Apr-23 at 01:45When you get to the 5th call:
QUESTION
My goal is to convert React-Native stack navigator from version 4-5. I've been running into some challenges and any help would be deeply appreciated.
ERROR: "The action 'NAVIGATE' with payload {"name":"Auth"} was not handled by any navigator. Do you have a screen named 'Auth'? If you're trying to navigate to a screen in a nested navigator, see https://reactnavigation.org/docs/nesting-navigators.html#navigating-to-a-screen-in-a-nested-navigator."
Nav flow: To authenticate user (with firebase) and go to a component that contains an already functional bottom-tab-navigator. Loading screen -> login -> sign up -> in the app (as a component).
This navigator is in the app.jsx file, here is the code. Note: I commented out the v4 stack-navigators, which work fine. Again, I want to convert this to the latest version 5.
...ANSWER
Answered 2020-Mar-08 at 06:03Create Auth Stack
QUESTION
Although I have no code to show or examples to present to you, I am in desperate need to learn how to play a video file on python and for it to quit once it ends to carry on any the program that is written afterwards.
Sorry in advance if this question doesn't follow stack overflows policies on a "good" question but it sparked my interest to query it.
Please reply to this with your ideas and topics I can research to gain a further understanding of it.
...ANSWER
Answered 2019-Nov-22 at 07:51OpenCV Should allow you what you want to do using the cv2.VideoCapture('file') function.
Here is a code example:
QUESTION
So this trivial question has generated a disproportionate amount of discussion here. It feels more like a playful puzzle but not full-on codegolf.
The javadoc for the NIO.2 Path class includes this part:
A Path is considered to be an empty path if it consists solely of one name element that is empty.
followed by the "empty path maps to default directory" clause -- that behavior is well understood and not relevant to the question here.
The discussion arose from some of our junior developers asking: given a Path instance p, how should they test for an empty path condition? Turns out the rest of their team (with more experience) had each been doing their own thing, and while all of their approaches "worked", they wanted to converge on the officially correct way; I believe there may have been a
round of beers at stake.
Testing for consists solely of one name element is trivial (
p.getNameCount() == 1). Testing for that is empty means obtaining that name element (p.getName(0)orp.getFileName()), which... is also aPathinstance that needs to be tested for emptiness...Calling
p.toString()and then testing forisEmpty()felt distasteful, because the emptiness test is being done on a String representation of the path, not the path instance itself. This sparked some philosophical debate about the completeness of the Path API and the meaning of canonical representations. I think they were already two beers in by then.One developer pointed to the
Path#resolve(Path other)method's javadocs, which contain the noteIf
So his emptiness test uses an isolatedotheris an empty path then this method trivially returns this path.Pathinstance, and tests forisolated.resolve(p).equals(isolated), which seemed suspiciously too clever and apparently led to raised voices.Another developer admitted to testing whether
pwas an instance ofsun.nio.fs.UnixPathand then abusing reflection to accessing its privateisEmpty()method. I wasn't present to ask what he does for Windows platforms, and suspect this wouldn't work in Java 9+ anyway.
In the end, they said they grudgingly settled on p.toString().length() == 0 but nobody was happy about it. None of them like the idea that the Path class depends on an "emptiness" quality that they could only apparently measure using methods of the String class, either before construction or after conversion. Presumably this solution was good enough for them to figure out who bought the beers, anyway.
Anyhow, once I heard about it I had to admit I was at a loss as to the best practice. What do the experts do for this case? Convert to String and be done with it, or stay within the NIO.2 API and take advantage of the resolve behavior, or...? (If you live near our other team, they might buy you a beer.)
ANSWER
Answered 2019-Nov-07 at 20:25Ideally, toString() should not be used for overall comparisons. And while you could use the resolve method, you really shouldn’t. (I won’t even address the use of reflection for this.)
I believe you all are over-thinking this problem. Just write what you mean. If you want to test if a Path is equal to the empty path, then do exactly that:
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