{key: val for key, val in dictionaryOne.items() if "aa" in val}

The best way to filter a dictionary in Python

您可以这样做来确定您的值是否具有aa。我假设您只需要打印bool值

is_exist = False
for key, val in dictionaryOne.items():
    if 'aa' in val:
        is_exist = True
    print(f'{key}: {is_exist}')

更新：

# Gets user input
name = input("enter the key: ")

dictionaryOne = { "ABCD" : "aatttgggtcatcg", "SSEE" : "atgcccgta", "GTAD" : "atgccggaaa" }

try:
    val = True if 'aa' in dictionaryOne.get(name) else False    
    print(val)
except Exception as k:
    print(k)