I am learning Python programming language. Currently
I am experimenting i-o files. I imported sys module and
in sys.path list I saw two kinds of paths:
/data/data/org.qpython.qpy3....
/storage/sdcard0/qpthon...
The former path does not exist physically on my device
(Tablet), although I can create/read files using this
path through python.
I want to know about these paths.
What are they called?
What are they for? etc.
The first path, /data/data/org.qpython.qpy3, this is where the actual QPython app is stored on your device. I don't believe you can access this path without having root access.
The second path, /storage/sdcard0/qpthon, this is where QPython saves files by default. It uses this location because it can be easily accessed with normal user privileges.
Related
Let's say I have a file called hello.txt in the folder called coding, and I want to open that in python. I know that if I don't use os, I would have to write open("coding/hello.txt") but if I would write os.open would I still have to specify the folder like ("coding/hello.txt") or can I just write os.open("hello.txt") because I am using os?
"File" and "operating system" can mean a lot of different things, but typically operating systems have the concept of a "current" or "working" directory. Each process has its own current directory, and if you don't specify a directory for a file it uses the current directory.
Do not rely on this. Too many things can change the current directory unexpectedly, and your program will suddenly start using a different file.
Instead always specify the full file path like open("/usr/tmp/coding/hello.txt") or whatever is appropriate for your operating system; it will probably provide environment variables or something for the user's home or temporary directories.
Note that your examples "coding/hello.txt" and "hello.txt" both use the current directory, and are different files.
At some point in my C program I have to deal with something like this.
FILE * fptr = fopen("/Parent/child/.../file.dat");
Which means in order to access any file I need to know it's location. That's all understandable.
But, how can I make this generic? In my computer "/Parent/child/.../file.dat" will work because that's where the file is stored, but I'm making a software to distribute to other users so the path obviously differs. My question is, how can I install a specific file into the user's computer such that I can know and get the location of that file. I a but confused about this concept so any resources that could help me understand it better would be greatly appreciated.
In Linux the default path to application files should be hardcoded. There is a standard which applications should follow. For example, architecture-independent files should go to /usr/share/ and then either your application name or, if you expect the data to be shared between applications, a generic category such as images. User-specific configuration files should go $HOME/.config/<app-name>. Older applications place their default configuration in $HOME/.<app-name> instead.
You should also provide an ability to override the default path to the data with a command line switch and/or an environment variable and/or a user configuration file (the location of the latter should also be overridable with a command line switch and/or an environment variable).
Some applications search for their data directory relatively to the executable position. An executable can know its own absolute path by reading /proc/self/exe symbolic link. For example, if an executable finds itself in /usr/local/bin/somename, it can look for /usr/local/share/<app-name> (two levels up from the executable name and down to share/<app-name>.).
Finally, if you distribute source code for the users to build, the file locations should be configuration parameters.
Many commands access files, and they usually take a path relative to ~/ which I gather is the "home" directory. In my case, C:\Users\Grant\AppData\Roaming\ which is where .emacs.d\ and my init files live.
This is great for Emacs, but not as useful for me. I typically would be over in C:\Users\Grant\Documents\ or my Python script files directory.
Also, I'm using Customize and typing in absolute file names for things like Org capture templates (currently anything I capture goes into files in one particular directory). Not that it's likely that these locations will change, but I was wondering if there are variables I can set for these places, which I can use in Customize or when invoking Dired - maybe some sort of environment variable? And if so, how can I refer to them when typing in a file name?
I am currently trying to create a plugin-like library for my company.
I need to check if four directories exist within the project structure. As java.io.File is not available, I am pretty confused on how to check for existance of a file that needs to exist within the project structure?
The concrete use-case.
There will be four directories:
/entities
/converter
/attributes
/caches
Now if the developer uses this library and wants to access all, lets say "Person"-Entities from the server, he should be able to call
RestGet.getAll("Person");
and the library looks in the source directory of the project if there are these Files:
/entities/PersonEntity.java //<-- Stores the actual data
/converter/PersonConverter.java //<-- Converts the JSON answer of the server to the Object
/attributes/PersonAttributes.java //<-- An enum that is used to set the attributes of the object
/caches/PersonCache.java //<-- A simple Cache
How can I do this? I tried with FileSystemStorage, but it only tell me that I should use getAppHome()...
I don't quite understand the usage of the source directory which obviously won't exist on the device where your application is running.
You can get access to files in the root of your SRC directory which get packaged into the JAR using Display.getInstance().getResourceAsStream(...).
The replacement to java.io.File is FileSystemStorage which is covered in the developer guide.
I have started coding an FTP client application (for fun). I’m trying to represent remotely hosted files with icons. For example, let’s say I’m browsing the root folder of an FTP server (/) and want to display the Backup.zip file with the icon association from that client operating system. On some systems, this may be the windows compression icon and other operating systems this may be WinZip or WinRAR icons.
I have the client browsing local files with the SHGetFileInfo() function. This works great with files that are local, however, this function requires the physical file in order to retrieve the associated icon. So, this will not work with remotely hosted files. I have found some samples of loading icons given a file extension, and this is really where the question comes in... What would be the best strategy to get icons associated to remote files?
Go to the registry every time and look up extension to icon associations
Create 1 byte files with each extension and use the SHGetFileInfo() function for remote files (using local 1 byte files as association for remote files)
Other strategies???
What would a professional software company creating an FTP client do?
Thank you for your time.
-Jessy Houle
I suggest that you don't go to the registry every time: go if you need to, but if you've already been for a given filetype then remember/cache that result (within your program) and reuse it.
Use the procedure here from a previous Stack Overflow question on the same idea and uses the registry instead of an actual file.
How can I get the filetype icon that Windows Explorer shows?