First of all:
iter() normally is a function. Your code masks the function by using a local variable with the same name. You can do this with any built-in Python object.
In other words, you are not using the
iter() function here. You are using a for loop variable that happens to use the same name. You could have called it
dict and it would be no more about dictionaries than it is about Guido’s choice of coffee. From the perspective of the
for loop, there is no difference between your two examples.
You’d otherwise use the
iter() function to produce an iterator type; an object that has a
.next() method (
.__next__() in Python 3).
for loop does this for you, normally. When using an object that can produce an iterator, the
for statement will use the C equivalent of calling
iter() on it. You would only use
iter() if you were doing other iterator-specific stuff with the object.