I used this script to add some tags on my obsidian vault, it's useful if you just imported stuff from notion-like websited, and you are trying to migrate to obsidian

string_appender.py

#diary #pensieri
import os

def add_tag(file_name):
    with open(file_name, 'r+') as f:
        content = f.read()
        f.seek(0, 0)
        
        # if a string is in the file then print helloworld

        if "Tipologia: Diario" in content:
            f.write("#diary #pensieri\n" + content)
        else:
            f.write("#pensieri\n" + content)

def main():
    # transverse currect directory
    for root, dirs, files in os.walk("."):

        for file in files:
            
            print(file)
            add_tag(file)

        break;

    # create a file

if __name__ == '__main__':
    main()