Open a file in VS code using `open -r`

I was trying to use the command code -r file_name.py in the integrated terminal in VS code to open the file in the existing window that I'd already opened. However, another new VS code window was still generated. What's weird is that originally, I could open a file by simply using code file_name.py without using the -r flag. Is there any way to solve the problem? I want the file to be opened in a new tab in the same window instead of in a new window. Any experience shared will be appreciated!