The with keyword triggers a context manager. Context managers automatically set up and take down data connections, or any other kind of object that implements the magic methods __enter__ and __exit__.
with open("test.txt", "r") as file:
do_things(file)file when the with block exits, so you never have to manually do a file.close(). Most connection types, including file readers and database connections, support this.
For more information, read the official docs, watch Corey Schafer\'s context manager video, or see PEP 343.