Q:

Looking if a Value(in a list) is in a dictionary

I have this dictionary with keys and values but I have more values added to a key.
dictionary = {"Key": ["Wauw", "Wow","What"], "Key2": ["Pretty", "Weak"]}
"Wauw" in dictionary

This doesn't work

A:

The shortest Version without import would be:
>>> dictionary = {"Key": ["Wauw", "Wow","What"], "Key2": ["Pretty", "Weak"]}
>>> 'Wauw' in [x for v in dictionary.values() for x in v]
True

# The list comrehensions result:
>>> print( [x for v in dictionary.values() for x in v] )
['Wauw', 'Wow', 'What', 'Pretty', 'Weak']

Another possibility would be:
>>> any(['Wauw' in lst for lst in dictionary.values()])
True

As there was a little performance question I tested the different versions for their execution speed:
# List-Comprehension: 'Wauw' in [x for v in dictionary.values() for x in v]
python -m timeit -s 'dictionary = {"Key": ["Wauw", "Wow","What"], "Key2": ["Pretty", "Weak"]}' "'Wauw' in [x for v in dictionary.values() for x in v]"
1000000 loops, best of 3: 0.398 usec per loop

# Generator: (x for v in dictionary.values() for x in v)
python -m timeit -s 'dictionary = {"Key": ["Wauw", "Wow","What"], "Key2": ["Pretty", "Weak"]}' "'Wauw' in (x for v in dictionary.values() for x in v)"
1000000 loops, best of 3: 0.639 usec per loop

# any(['Wauw' in lst for lst in dictionary.values()])
python -m timeit -s 'dictionary = {"Key": ["Wauw", "Wow","What"], "Key2": ["Pretty", "Weak"]}' "any(['Wauw' in lst for lst in dictionary.values()])"
1000000 loops, best of 3: 0.272 usec per loop

# Itertools version from user8408080 without measuring the import
python -m timeit -s 'from itertools import chain;dictionary = {"Key": ["Wauw", "Wow","What"], "Key2": ["Pretty", "Weak"]}' "'Wauw' in chain(*dictionary.values())"
1000000 loops, best of 3: 0.33 usec per loop

# Itertools version from user8408080 import is recognized in the measuring
python -m timeit -s 'dictionary = {"Key": ["Wauw", "Wow","What"], "Key2": ["Pretty", "Weak"]}' "from itertools import chain; 'Wauw' in chain(*dictionary.values())"
1000000 loops, best of 3: 1.02 usec per loop

