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

[Gribouillis]

Though I wonder why it works if it's out of the class?

That's the way scopes work in Python, or rather namespaces. Inside a method, the names that are defined in the class are not directly available.

foo = 1  # name in the **global** namespace

class Spam:
    bar = 2  # in the namespace of the class body

    def method(self):
        qux = 3 # in the method's **local** namespace

        print(qux) # works. We see the local namespace
        print(foo) # also works. We see the global namespace
        print(bar) # doesn't work. We don't see the class' namespace
        print(self.bar) # works. We can access the class' members through the instance self.