Paths Workdir.

In Code Lab your code runs in a virtual folder lab (working directory). A relative path "hello.txt" is a file in that folder — not on your PC.

with open("hello.txt", encoding="utf-8") as f: line = f.readline()

readline() returns one line (with \n). strip() removes whitespace and the newline.

print(line.strip())

open() as a context manager closes the file for you. encoding="utf-8" is good practice for text.