why does TemporaryDirectory change type within a "with" block?

In python3 console

>>> x1=tempfile.TemporaryDirectory()
>>> print(type(x1))
<class 'tempfile.TemporaryDirectory'>
>>> with tempfile.TemporaryDirectory() as x2:
...   print(type(x2))
... 
<class 'str'>

Why is x1 a TemporaryDirectory and x2 a str?

>Solution :

Because with foo() as x has x take on the value of foo().__enter__()‘s return value.

x = foo() is a different thing.

See here for the implementation of TemporaryDirectory; it does a bunch of things, but the important thing is that entering the context manager returns the directory name, and exiting the context manager destroys that named directory.

class TemporaryDirectory:
   ...

    def __enter__(self):
        return self.name

   ...