def encode(word):
# a dictionnary for all possible symbol
symbols = {}
# counts the number of occurences each symbol
for letter in word:
if letter in symbols:
symbols[letter] += 1
else :
symbols[letter] = 1
# here we construct the binary tree with tuples :
tree = buildTree(symbols)
# we have to return the tree too for decoding later
# we could encode it better, but its native string representation is ok
treeString = str(tree)
treeString = treeString.replace(", ", ",")
# the code we'll return, which first contains the length taken by the tree
code = BitStream(12)
code.int = len(treeString)
# then we add the tree to the code
codedTree = BitArray(8 * len(treeString))
codedTree.bytes = treeString
code.append(codedTree)
# a recursive traversal of the tree allows us to create a dictionnary of matching symbols and codes for encoding :
symbols = buildEncodingDict(tree)
# finally we encode the word
codedWord = encodeWithDict(symbols, word)
code.append(codedWord)
return code
