dict elements are sometimes treated as List and sometimes as String

[phython_mdr]

I'm just learning Python by developing an anagram finder.

After a bit of debugging it seems that if I check "if token not in words" then the words dictionary treats its elements as List items.

But if I assign a value without doing the "if" check, the values are treated as Strings (rather than a List of strings).

Is there somewhere I can research why the behavior changes? Is there a way to force the dictionary to make the values Lists?

I'm using PyCharm 2019.3.4 for Mac with Python 3.7.2

# This code block treats words[] values as List items, allowing append to work
words = dict()
token: str ="acto"
if token not in words:
    words[token] = ["coat"]
else:
    words[token].append("coat")

words[token].append("taco") #In this code block, "taco" is appended to the List associated with the "acto" key -> ['coat', 'taco']

for x in words:
    print (words[x])

# This code block treats words[] values as Strings items.  Append does not work
words = dict()
token: str ="acto"
words[token] = ["coat"]
words[token].append("taco") #blows up because String has no append method.