ModuleNotFoundError: No module named 'sqlalchemy'

from sqlalchemy import create_engine, Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

engine = create_engine('sqlite:///users.db', echo=False)
Session = sessionmaker(bind=engine)
session = Session()
Base = declarative_base()

class User(Base):
    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)
    name = Column(String)
    fullname = Column(String)
    nickname = Column(String)

    def __repr__(self): 
        return f'<User(name={self.name}, fullname={self.fullname}, nickname={self.nickname})>'


if __name__ == '__main__': 
    Base.metadata.create_all(engine)