为何Python REPL环境中sys.path的首个元素为空字符串？

Great question! Let me break down this behavior clearly for you:

First, let's recap what sys.path does: it's the list of directories Python searches through when you try to import a module. Python checks these paths in order, so the first entry has the highest priority.

What the empty string "" means #

The empty string in sys.path is a special entry that tells Python to look in your current working directory (the folder you were in when you launched the REPL).

Why REPL uses this instead of a directory path #

The difference between REPL and running a script is key here:

• When you run a Python script (e.g., python my_script.py), Python sets the first entry in sys.path to the directory where the script lives. This makes sense because scripts often need to import other modules from the same folder as the script itself.
• But in the REPL, there's no "script file" to anchor the path. You're working interactively, so Python assumes you'll want to import modules from the folder you're currently working in. Using the empty string is Python's way of saying "check the current directory first" without hardcoding a specific path (since your current working directory can change even during a REPL session).

For example: if you start the REPL from /users/you/my_projects, and that folder has a file utils.py, you can just run import utils directly—this works because the empty string in sys.path points to /users/you/my_projects.

This design choice makes the interactive REPL experience much smoother, as you don't have to manually add your working directory to sys.path every time you want to test a local module.

内容的提问来源于stack exchange，提问作者daparic