File Handling - General Questions

What does f.seek(0) do?

What is the output of the following code?

import io
f = io.StringIO('a\nb\nc\n')
print(len(f.readlines()))

Which module is used to read and write CSV files?

Which mode opens a file for appending?

What is the output of the following code?

import io
f = io.StringIO('hello\nworld\n')
print(f.readline().strip(), f.readline().strip())