Looping through a dictionary for every other value

[Mekire]

That is a dictionary comprehension. Comprehensions are pretty natural once you are into python but can be a bit arcane when you first start.

So, lets start with the iteration.
If we have a dict:

>>> a = {"a" : 1, "b" : 2, "c" : 3}

We can get tuples of the key:value pairs with items()

>>> list(a.items())
[('a', 1), ('c', 3), ('b', 2)]

So we can iterate through these tuples:

>>> for k,v in a.items():
...     print(k,v)
...
('a', 1)
('c', 3)
('b', 2)
>>>

So making the dict without the comprehension:

>>> b = {} # make an empty dict
>>> for k,v in a.items():
...     if v % 2: # is the value odd
...         b[k] = v # set key to value
...
>>> b
{'a': 1, 'c': 3}

And with the comprehension it is much more concise:

>>> c = {k:v for k,v in a.items() if v % 2}
>>> c
{'a': 1, 'c': 3}