Saving text file with a click: valueerror i/o operation on closed file

[Gribouillis]

For the first question, you still have the error because you must not indent the

@contextmanager
def redirect_stdout(file):
    ...

Don't write this definition in a class, write it at module level outside of any class and without indentation.

If you want to print simultaneously to the file and to the console, here is an updated version

from contextlib import contextmanager
import sys

@contextmanager
def redirect_stdout(file):
    old, sys.stdout = sys.stdout, file
    try:
        yield
    finally:
        sys.stdout = old

class FileTee:
    """Stores a sequence of file objects to allow printing to several files at a time"""
    def __init__(self, ifile):
        self.ifile = list(ifile)
        
    def write(self, s):
        for f in self.ifile:
            f.write(s)

def main():
    with open('foo.txt', 'w') as file, redirect_stdout(
        FileTee([sys.stdout, file])):
        print('Hello there!')
    print('Done')

if __name__ == '__main__':
    main()