# Lempel-Ziv-Welch (LZW) algorithme en Python – LZW compression

J’ai utilisé le code suivant que j’a! trouvé sur Website rosettacode.org

```def compress(uncompressed):
"""Compress a string to a list of output symbols."""

# Build the dictionary.
dict_size = 256
dictionary = dict((chr(i), i) for i in range(dict_size))
# in Python 3: dictionary = {chr(i): i for i in range(dict_size)}

w = ""
result = []
for c in uncompressed:
wc = w + c
if wc in dictionary:
w = wc
else:
result.append(dictionary[w])
# Add wc to the dictionary.
dictionary[wc] = dict_size
dict_size += 1
w = c

# Output the code for w.
if w:
result.append(dictionary[w])
return result

def decompress(compressed):
"""Decompress a list of output ks to a string."""
from io import StringIO

# Build the dictionary.
dict_size = 256
dictionary = dict((i, chr(i)) for i in range(dict_size))
# in Python 3: dictionary = {i: chr(i) for i in range(dict_size)}

# use StringIO, otherwise this becomes O(N^2)
# due to string concatenation in a loop
result = StringIO()
w = chr(compressed.pop(0))
result.write(w)
for k in compressed:
if k in dictionary:
entry = dictionary[k]
elif k == dict_size:
entry = w + w[0]
else:
raise ValueError('Bad compressed k: %s' % k)
result.write(entry)

# Add w+entry[0] to the dictionary.
dictionary[dict_size] = w + entry[0]
dict_size += 1

w = entry
return result.getvalue()

# How to use:
compressed = compress('TOBEORNOTTOBEORTOBEORNOT')
print (compressed)
decompressed = decompress(compressed)
print (decompressed)```

La taille de chaque fichier est la même avec chaque fichier, sans nouvel espace

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