Finding the second level keys of a multi key dictionary Python?

Question

I have a multi key dict in the following format. I am trying to access the list of the second level keys, however, it is returning the keys in the format of a dict_keys list. What I am trying to get is ['a', 'b', 'c', 'd', 'e', 'f']

dictTest={}
dictTest[1]={'a':1, 'b':2}
dictTest[2]={'c':1, 'd':2}
dictTest[3]={'e':1, 'f':2}
print(dictTest)
print(list([dictTest[i].keys() for i in dictTest.keys()]))         
{1: {'a': 1, 'b': 2}, 2: {'c': 1, 'd': 2}, 3: {'e': 1, 'f': 2}}
[dict_keys(['a', 'b']), dict_keys(['c', 'd']), dict_keys(['e', 'f'])]

Answer 1

Try this:

# sum([list(b.keys()) for b in dictTest.values()], [])
# syntax improvement by @wwii
sum([list(b) for b in dictTest.values()], [])

Output:

['a', 'b', 'c', 'd', 'e', 'f']

Answer 2

You could use itertools.chain in combination with mapping dict.keys to all the dicts values:

from itertools import chain

dictTest = {1: {'a': 1, 'b': 2}, 2: {'c': 1, 'd': 2}, 3: {'e': 1, 'f': 2}}

print(list(chain(*map(dict.keys, dictTest.values()))))

---

['a', 'b', 'c', 'd', 'e', 'f']

Answer 3

>>> [v2 for v1 in dictTest.values() for v2 in v1] ['a', 'b', 'c', 'd', 'e', 'f']