Python3 implementation of Unix tree command. Runs on Windows and Nix

tree.py

import os
# mimic Unix tree command in python
# runs on Windows and Nix
# run from current directory for tree output
def tree(cwd):
    print(f"+ {cwd}")
    for root, dirs, files in os.walk(cwd):
        level = root.replace(cwd, '').count(os.sep)
        indent = ' ' * 4 * (level)
        print(f"{indent}+ {os.path.basename(root)}/")
        sub_indent = ' ' * 4 * (level + 1)
        for file in files:
            print(f"{sub_indent}- {file}")
if __name__ == '__main__':
    tree('.')