FileNotFoundError: [Errno 2] No such file or directory: '/tmp/...'

The error

$ echo hello > /tmp/notes.txt
$ python -c "print(open('/tmp/notes.txt').read())"
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/notes.txt'

The same happens with /c/Users/you/..., Git Bash's name for C:\Users\you.

Why it happens

• The paths are Git Bash's own. Git Bash shows your drives as /c/, /d/ and so on, and /tmp is its name for your Windows temp folder (C:\Users\you\AppData\Local\Temp).
• Windows Python doesn't know them. To Python, /tmp/notes.txt means C:\tmp\notes.txt, and /c/Users means C:\c\Users. Neither exists.
• Git Bash only converts arguments. When an argument looks like a path, Git Bash rewrites it before Python starts. A path inside your code is just text, so it gets through unchanged.

The fix

Any of these works:

• Write the Windows path in the code. Forward slashes are fine: open('C:/Users/you/AppData/Local/Temp/notes.txt').
• Convert it first. cygpath -m /tmp/notes.txt prints C:/Users/you/AppData/Local/Temp/notes.txt.
• Pass the path as an argument. Git Bash converts it on the way in:

  $ python -c "import sys; print(sys.argv[1])" /tmp/notes.txt
  C:/Users/you/AppData/Local/Temp/notes.txt

• Use a path relative to the current folder, which means the same in both.