Does tmpdir in pytest create a file only when we write to it?

Question

When I use fp = tmpdir.join("hello.txt") in pytest, does pytest actually create a file in my temp directory or it creates only when I write fp.write("hello") ?

Answer 1

No, pytest will not create the file until you actually write to it. Under the hood, as mentioned in the documentation, tmpdir uses py.path . When you call join it will lazily get the new path, meaning it does not exist until you actually write something to it.