You use double looping:
[i for k, v in sorted(d.iteritems()) for i in (k, v)]
or
[i for item in sorted(d.iteritems()) for i in item]
or itertools.chain.from_iterable()
:
from itertools import chain
list(chain.from_iterable(item for item in sorted(d.iteritems())))
although you could just use:
list(chain.from_iterable(sorted(d.iteritems())))
in these cases.
Demo:
>>> d = {'pKey_b': 'vb1', 'pKey_e': 've1', 'pKey_c': 'vc1', 'pKey_a': 'va1', 'pKey_d': 'vd1'}
>>> [i for k, v in sorted(d.iteritems()) for i in (k, v)]
['pKey_a', 'va1', 'pKey_b', 'vb1', 'pKey_c', 'vc1', 'pKey_d', 'vd1', 'pKey_e', 've1']
>>> from itertools import chain
>>> list(chain.from_iterable(item for item in sorted(d.iteritems())))
['pKey_a', 'va1', 'pKey_b', 'vb1', 'pKey_c', 'vc1', 'pKey_d', 'vd1', 'pKey_e', 've1']
>>> list(chain.from_iterable(sorted(d.iteritems())))
['pKey_a', 'va1', 'pKey_b', 'vb1', 'pKey_c', 'vc1', 'pKey_d', 'vd1', 'pKey_e', 've1']