python - Detect most likely words from text without spaces / combined words

Question

How could I detect and split words from a combined string?

Example:

"cdimage" -> ["cd", "image"]
"filesaveas" -> ["file", "save", "as"]

Answer 1

Here's a dynamic programming solution (implemented as a memoized function). Given a dictionary of words with their frequencies, it splits the input text at the positions that give the overall most likely phrase. You'll have to find a real wordlist, but I included some made-up frequencies for a simple test.

WORD_FREQUENCIES = {
    'file': 0.00123,
    'files': 0.00124,
    'save': 0.002,
    'ave': 0.00001,
    'as': 0.00555
}

def split_text(text, word_frequencies, cache):
    if text in cache:
        return cache[text]
    if not text:
        return 1, []
    best_freq, best_split = 0, []
    for i in xrange(1, len(text) + 1):
        word, remainder = text[:i], text[i:]
        freq = word_frequencies.get(word, None)
        if freq:
            remainder_freq, remainder = split_text(
                    remainder, word_frequencies, cache)
            freq *= remainder_freq
            if freq > best_freq:
                best_freq = freq
                best_split = [word] + remainder
    cache[text] = (best_freq, best_split)
    return cache[text]

print split_text('filesaveas', WORD_FREQUENCIES, {})

--> (1.3653e-08, ['file', 'save', 'as'])