Why don't f-strings change when variables they reference change?

Question

While playing with new f-strings in the recent Python 3.6 release, I\'ve noticed the following:

1. We create a foo variable with value bar

Answer 1

Strings are immutable and once a string is created, it can no longer be changed.

foo and more importantly baz are both strings. That means when you create them they go into memory and can no longer be changed.

Once you assigned foo = bar you created this object and assigned it to a specific location in memory. Same thing was done with baz.

Even though baz was as a Format string literal does not mean that it is no longer immutable since:

In [4]: type(baz)
Out[4]: str

By doing so, baz was created as an object and assigned to your memory as Hanging on in bar, thus its relation to foo is purely during instantiation. During which baz seeks the object foo and concatenate it where appropriate.

Once you created foo = 'spam' you destroyed the original assignment of foo and create a new one in memory.