this is about C++ coding in CERN ROOT.
So I have a text file with columns of data. Now I need to make a .root file with all the data in a tree. How would I do this? Also, if the text file has column headers, how would I write my code to get them to be my tree's branch names?
Thanks in advance!
this example from the ROOT web page shows how to do exactly what you want:
http://root.cern.ch/root/html534/tutorials/tree/cernbuild.C.html
There is a TTree method for that: http://root.cern.ch/root/html/TTree.html#TTree:ReadFile
To use the reader as branch names you have to be a bit more creative. Read the line, parse it and use it as a branch descriptor in the TTree:ReadFile call.
Related
I have a use case where I want to read the filename from a metadata table, I have written a pipeline function to read the metadata table, but I am not sure how can I pass this information to ReadFromText as it only takes string as input, Is it possible to assign this value to ReadFromText(). Please suggest some workarounds or ideas how to achieve this, Thanks
code: pipeline | 'Read from a File' >> ReadFromText(I want to pass the file path here?,
skip_header_lines=1)
Note: There will be various folders and files in storage, files are in csv format, but in my use case I can't directly pass the storage location or filename to file path in ReadFromText. I want to read it from metadata and pass the value. Hope I am clear, Thanks
I don't understand why you need to read the metadata. If you want to read all the files inside a folder, you can just provide a blob. This solution working in python, not sure about java.
p|readfromtext("./folder/*.csv")
"*" is the blob here, which allows pipeline to read all the patterns matching .csv. You can also add something at the starting.
What you want is textio.ReadAllFromText which reads from a PCollection instead of taking a string directly.
I have a program that create a text file of stock items, which contains detail of 'total production' , 'stock remaining' and so on. Now my question is how do I edit that text file with my program. For example if I mistake to enter a correct data (like production was 500 pieces but enter only 400) now how can I edit my file to make it correct without effecting other data.
You probably should not create a text file in the first place. Did you consider using sqlite (or indexed files à la GDBM ...) or some real database like PostgreSQL or MongoDb?
If you insist on editing programmatically a textual file, the only way is to process every line : either keep all of them in memory, or copy them (except the one you'll change) to some new file.... But there is no portable way to change the content of a file in the middle.
You might also be interested in textual serialization formats like JSON, YAML (or maybe even XML).
I am not able to understand what actually parsing the html means ?
As i understand -
- it means that suppose we have any html file by parsing we can have the contents of the html file and we can edit them using parsing. Am i right ?? (parsing simply gives the idea about the contents and structure inside the file.)
I have one more question-
- I also want to know that suppose i have html file contents stored in a stream suppose (inside IStream *HTMLContents - No matter for now that how i got these contents). Is there any process exist that using these file contents may i create the preview on any window/Dialog Box/Preview pane with the same way exactly as i get the view of that html file in the browser.(for now you can imagine that i have downloded the HTML File contents from any web page(or from any where-No matter- But i have contents of html file in my stream i am sure about it) and i want to render that html file view in my own created window/Dialog Box/Preview pane(i mean it should view exactly as it appears in browser-Yes i know it won't be avle to display some pictures in html file but thats not a problem for me). How to do that ?? (I am using Visual c++ for my accomplishing my task)
Parsing basically means analyzing any data. When you parse HTML, it could be that you are figuring out where all the various elements are located and what do they do.
As for displaying HTML, it depends on what do you want to do:
If you want to open the file in your browser, use something like this.
As for displaying HTML directly in your form, I don't really know of any other way than parsing the HTML and creating your own web rendering engine. Good luck and have fun with that I guess.
Parse HTML means build object model such as DOM: https://en.wikipedia.org/wiki/Document_Object_Model in your program
As stated from my title, how can i delete a specify line from a textfile.
My program has a HR user, which they can edit/remove users information.
I am able to write into a file, but to delete from a specific line, i am clueless.
Hopefully someone can give me an example of how to do it, thanks !
A example of my textfile
user;pass;1234;John;1111
user1;pass1;2345;May;2222
user2;pass2;3456;Mary;3333
user3;pass3;4567;Andy;4444
hr;hr;5678;Jonathan;5555
admin;admin;6789;Aili;6666
user10;pass10;7890;eggy;9999
and so i want to delete the contents of user3 which is at line 4 of my textfile,when the user inputs the username, which is user3.
Here is a pseudocode, I will let you work out the details:
1. read the entire file into a vector
2. delete that file
3. create and write back the data to the file skipping the line that isn't required.
Use std::getline() in a loop to read a line from the file.
Load the file content into memory,
delete the line there,
and write the content back to file.
You could somewhat optimize this process by not loading the portion of the file before the line being deleted (though you'd still need to scan it to find the "target" line), but you won't be able to do much better than that without a specialized data structure.
If this is really important performance-wise, consider using a database instead of the plain file.
at the moment I'm writing a kind of lib, which gets from outside the file name 'sFilename'. With it data were written to a file it will be created, data were append to an existing file with data, data were updated in an existing file with data or the data were read from an existing data.
The user of the application with my lib should get as much as possible on information about errors of file handling.
For this purpose I code a method FileExists(...) which uses _stat() to determine if a file exists or not and a method "bool checkPermission(std::string sFilename, CFile::EOpenmode iOpenmode)" which gives back a bool if the specified file (sFilename) with the iOpenmode (Read, Write, Readwrite) have the permission to be read, written or read and written.
This method works with _stat(sFilename.c_str(), &buf) too and gives the desired information of the file back in buf.
Before checking any file I want to check if the directory containing the specified file has the desired permissions and for that I want to use the checkPermission method [works with _stat()] for the directory!
Now the problem: how can I determine easyly the containing directory? If the user just give a filename "test.txt" the file will be created or read in working directory. So its easy to get the up-directory. Its the same like the working directory. (And there its simple to use checkPermission to get detailed information about the directory).
But what about when the user not only give the file name? For exaample "....\test.txt" or "dir1\dir2\test.txt". How to combine the working directory with a specific path to gain the up-directory of the file and then to check the permissions?
Phew, I hope all is clear and it was'nt too long ;-)
Rumo
I'd suggest using the Boost FileSystem library at www.boost.org. In particular, check out the path class, which has methods such as make_absolute and parent_path.
This is Windows example code GetFileNameFromHandle to show you how to get the path from a HANDLE. I think it is what you are looking for.
http://msdn.microsoft.com/en-us/library/aa366789%28v=vs.85%29.aspx
I found out that _stat() and _access() doesn't really works for the permissions of the directories. See this stackoverflow page.
With _stat() you can't use ".\" to get information about the current directory. But _access() at least can check if a directory exists as well ".\" or "..\".
In conclusion I use _access() to check the existence of a directory and _stat() to check the permissions of an existing file. If a file should be created I'll check it by doing.
And by the way ;-) I don't need to combine working directory with the user specified file because I can use the specified file alone in _access() to determine if directory exists.
Rumo