Implementing a Trie in Python using lists alone

I've been working on implementing a Trie in Python for educational purposes. I tried implementing one using dictionaries and I was successful; find below my attempt at implementing a trie using lists alone.

The structure of a trie with the words in, inn, inner, innerr would be as follows :-

[['i', [['n', [['n', [['e', [['r', [['r', [], 'end']], 'end']]]], 'end']], 'end']]]]

where end indicates the end of a word.

class TrieException(Exception):
    pass

def add_word(word, trie):
    END = "end"
    if word == '':
        raise TrieException("word empty")

    prev = None
    branch = trie

    for i, c in enumerate(word):
        found = False
        for each in branch:
            if each[0] == c:
                if i == len(word)-1:
                    if len(each) > 2:
                        raise TrieException("Word already present")
                    else:
                        each.append(END)
                prev = branch
                branch = each[1]
                found = True
                break
        if not found:
            nb = []
            if i == len(word)-1:
                branch.append([c, nb, END])
            else:
                branch.append([c, nb])
            branch = nb

def search_word(word, trie):
    if word == '':
        raise TrieException("empty word")

    branch = trie
    for i, c in enumerate(word):
        found = False
        for each in branch:
            if each[0] == c:
                found = True
                branch = each[1]
                if i == len(word)-1:
                    if len(each) <= 2:
                        raise TrieException("Word not found")
                break
        if not found:
            raise TrieException("Word not found")

Do you have any suggestions on how I do this in a more cleaner fashion?