How to reliably open a file in the same directory as the currently running script

I used to open files that were in the same directory as the currently running Python script by simply using a command like:

open("Some file.txt", "r")

However, I discovered that when the script was run in Windows by double-clicking it, it would try to open the file from the wrong directory.

Since then I’ve used a command of the form

open(os.path.join(sys.path[0], "Some file.txt"), "r")

whenever I wanted to open a file. This works for my particular usage, but I’m not sure if sys.path[0] might fail in some other use case.

So my question is: What is the best and most reliable way to open a file that’s in the same directory as the currently running Python script?

Here’s what I’ve been able to figure out so far:

• os.getcwd() and os.path.abspath('') return the “current working directory”, not the script directory.

• os.path.dirname(sys.argv[0]) and os.path.dirname(__file__) return the path used to call the script, which may be relative or even blank (if the script is in the cwd). Also, __file__ does not exist when the script is run in IDLE or PythonWin.

• sys.path[0] and os.path.abspath(os.path.dirname(sys.argv[0])) seem to return the script directory. I’m not sure if there’s any difference between these two.

Edit:

I just realized that what I want to do would be better described as “open a file in the same directory as the containing module”. In other words, if I import a module I wrote that’s in another directory, and that module opens a file, I want it to look for the file in the module’s directory. I don’t think anything I’ve found is able to do that…