LZW implementation via python

LZW.py

def Compress(s):
    dictionary = {chr(i):i for i in range(0,255)} # create dictionary according to ascii code
    last = 256 # the size of dictionary
    p = ""
    result = []
    for c in s:
        pc = p+c
        if pc in dictionary:
            p = pc # if pc in dictionary then try to append next character until pc is not in dictionary
        else:
            result.append(dictionary[p]) 
            dictionary[pc] = last # save pc's code
            last += 1 # increment the size of dictionary
            p = c
    if p != '':
        result.append(dictionary[p])
    return result

def Uncompress(arr):
    dictionary = {i:chr(i) for i in range(0,255)}
    last = 256
    result = []
    p = arr.pop(0) # get first element and pop it out
    result.append(dictionary[p])
    
    for c in arr:
        if c in dictionary:
            entry = dictionary[c]
        result.append(entry)
        dictionary[last] = dictionary[p] + entry[0] # append code
        last += 1 # increment the size of dictionary
        p = c # maintain the info of last character
    return result

def get_test_str(filename):
    with open(filename, 'r') as file:
        return file.read()
if __name__ == '__main__':
    test_str = get_test_str("google.html")
    compress_str = Compress(test_str)
    uncompress_str = Uncompress(compress_str)
    # print(compress_str, uncompress_str)
    print("filename: google_homepage.html")
    print "len of test string:", len(test_str)
    print "len of compressed string:", len(compress_str)
    print "compression ratio:", float(len(compress_str))/len(test_str)
    print "max element:", max(compress_str)