Python file descriptor is open

For instance, you order your code to close a file through your long lines of code. It shows an error like:. It means that the file defined in the program is already closed automatically while running the code. There lies no use in defining a separate method to perform the same task again. During such an error, you should look for possibilities where your file may get closed in your code. In python file descriptors are integers positive that do the job of identifying the open files kept in a table of files by the kernel.

They are generally non-negative values 0, 1, or 2. Bad file descriptor mainly arises due to many factors that were discussed in brief above.

The main fact is that they occur when the right functions do not perform in association with the file descriptors. With clear analysis and better knowledge of the concept, one can easily detect these errors and transform the code into a successful one.

IOError:[Errno 9] Bad file descriptor. What is a bad file descriptor? What is a standard file descriptor? What is Fcntl in Python? Notify of. Leaking file descriptors in child processes causes various annoying issues and is a known major security vulnerability. This PEP proposes to make all file descriptors created by Python non-inheritable by default to reduce the risk of these issues.

This PEP fixes also a race condition in multi-threaded applications on operating systems supporting atomic flags to create non-inheritable file descriptors. We are aware of the code breakage this is likely to cause, and doing it anyway for the good of mankind. Details in the section "Backward Compatibility" below. Each operating system handles the inheritance of file descriptors differently.

There is one exception: os. The reason is an implementation artifact: os. The issue proposes to change os. Using the spawnv function, all inheritable handles and all inheritable file descriptors are inherited in the child process.

So when at least one standard stream is replaced, all inheritable handles are inherited by the child process. Read Programmatically controlling which handles are inherited by new processes in Win32 Raymond Chen, Dec for more information.

This option works if all other handles are non-inheritable. The Python issue "Add an atfork module" proposes to add such lock, it can be used to make handles non-inheritable without the race condition. Such lock only protects against a race condition between Python threads; C threads are not protected. If the child program cannot be modified, an intermediate program can be used to steal handles from the parent process before spawning the final child program.

The intermediate program has to pass the handle from the child process to the parent process. The parent may have to close duplicated handles if all handles were not stolen, for example if the intermediate process fails. If the command line is used to pass the handle values, the command line must be modified when handles are duplicated, because their values are modified.

This PEP does not include a solution to this problem because there is no perfect solution working on all Windows versions. This point is deferred until use cases relying on handle or file descriptor inheritance on Windows are well known, so we can choose the best solution and carefully test its implementation. POSIX provides a close-on-exec flag on file descriptors to automatically close a file descriptor when the C function execv is called.

File descriptors with the close-on-exec flag cleared are inherited in the child process, file descriptors with the flag set are closed in the child process.

The flag can be set in two syscalls one to get current flags, a second to set new flags using fcntl :. NOTE: The close-on-exec flag has no effect on fork : all file descriptors are inherited by the child process. The Python issue "Add an atfork module" proposes to add a new atfork module to execute code at fork, which may be used to automatically close file descriptors. Most of the time, inheritable file descriptors "leaked" to child processes are not noticed, because they don't cause major bugs.

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