Use of yield with a dict comprehension

Question

As a contrived example:

myset = set([\'a\', \'b\', \'c\', \'d\'])
mydict = {item: (yield \'\'.join([item, \'s\'])) for item in myset}

and

Answer 1

I find! ^_^

In normal life, expression

print {item: (yield ''.join([item, 's'])) for item in myset} 

evaluate like this:

def d(myset):
    result = {}
    for item in myset:
        result[item] = (''.join([item, 's']))
    yield result

print d(myset).next()

Why yield result instead return result? I think it is necessary to support nested list comprehensions* like this:

print {i: f.lower() for i in nums for f in fruit}  # yes, it's works

So, would look like this code?

def d(myset):
    result = {}
    for item in myset:
        result[item] = (yield ''.join([item, 's']))
    yield result

and

>>> print list(d(myset))
['as', 'cs', 'bs', 'ds', {'a': None, 'b': None, 'c': None, 'd': None}]

First will be returned all values of ''.join([item, 's']) and the last will be returned dict result. Value of yield expression is None, so values in the result is None too.

* More correct interpretation of evaluate nested list comprehensions:

print {i: f.lower() for i in nums for f in fruit}

# eval like this:

result = {}
for i, f in product(nums, fruit): # product from itertools
    key, value = (i, f.lower())
    result[key] = value
print result