add LZW code/decode

455-Codage_Sources/algo_code/LZW.py

+#!/usr/bin/env python3
+
+import numpy as np
+
+univers = ['a','b','c']
+message = "aabababac"
+
+def code_LZW(message, univers):
+    msg = message
+    dictionnaire = dict(zip(univers,[i for i in range (len(univers))]))
+    w=""
+    code =[]
+    for c in msg:
+        wc = w+c
+        if wc in dictionnaire:
+            w =wc
+        else:
+            code.append(dictionnaire[w])
+            dictionnaire[wc] = len(dictionnaire)
+            w = c
+    if w:
+        code.append(dictionnaire[w])
+    return code,dictionnaire
+
+def decode_LZW(code,univers):
+    dictionnaire = dict(zip([i for i in range(len(univers))],univers))
+    w = dictionnaire[code.pop(0)]
+    msg = [w]
+    for k in code:
+        if k in dictionnaire:
+            entry = dictionnaire[k]
+        elif k == len(dictionnaire):
+            entry = w +w[0]
+        msg.append(entry)
+        dictionnaire[len(dictionnaire)] = w+entry[0]
+        w = entry
+    print(dictionnaire)
+    return ''.join(msg)
+
+
+code,dictionnaire = code_LZW(message,univers)
+print(code)
+print(dictionnaire)
+msg = decode_LZW(code, univers)
+print(message)
+print(msg)