如何在創建霍夫曼代碼時處理'/ n'，'/ t'和類似的ASCII密鑰

Question

對於我的項目，我必須使用霍夫曼算法壓縮文件。我想出了大部分部分，但是我很難處理其他ASCII字符，如換行符，製表符等。這是我迄今爲止所做的，但是在處理文件時我無法獲得其他字符創建。

import operator 

def getFreq(mylst): 
    dct = {'a':0,'b':0,'c':0,'d':0,'e':0,'f':0,'g':0,'h':0,'i':0,'j':0,'k':0,'l':0, 
     'm':0,'n':0,'o':0,'p':0,'q':0,'r':0,'s':0,'t':0,'u':0,'v':0,'w':0,'x':0,'y':0,'z':0,' ':0, 
     'A':0,'B':0,'C':0,'D':0,'E':0,'F':0,'G':0,'H':0,'I':0,'J':0,'K':0,'L':0, 
     'M':0,'N':0,'O':0,'P':0,'Q':0,'R':0,'S':0,'T':0,'U':0,'V':0,'W':0,'X':0,'Y':0,'Z':0,'.':0,',':0, 
     '1':0,'2':0,'3':0,'4':0,'5':0,'6':0,'7':0,'8':0,'9':0,'0':0, '-':0,'(':0, ')':0} 

    for k, v in dct.items(): 
     for i in mylst: 
      if i == k: 
       dct[k] += 1 
       up_dct = sorted(dct.items(), key=operator.itemgetter(1), reverse=True) 

    srt_dct = dict((k, v) for k, v in up_dct) 

    return srt_dct 


def assign_code(nodes, label, result, prefix = ''): 
    childs = nodes[label] 
    tree = {} 
    if len(childs) == 2: 
     tree['0'] = assign_code(nodes, childs[0], result, prefix+'0') 
     tree['1'] = assign_code(nodes, childs[1], result, prefix+'1') 
     return tree 
    else: 
     result[label] = prefix 
     return label 

def Huffman_code(_vals): 
    vals = _vals.copy() 
    nodes = {} 
    for n in vals.keys(): # leafs initialization 
     nodes[n] = [] 

    while len(vals) > 1: # binary tree creation 
     s_vals = sorted(vals.items(), key=lambda x:x[1]) 
     a1 = s_vals[0][0] 
     a2 = s_vals[1][0] 
     vals[a1+a2] = vals.pop(a1) + vals.pop(a2) 
     nodes[a1+a2] = [a1, a2] 
    code = {} 
    root = a1+a2 
    tree = {} 
    tree = assign_code(nodes, root, code) # assignment of the code for the given binary tree 
    return code, tree 

r_file = open('test.txt', 'r') 

ro = r_file.read() 


lst = list(ro) 

freq = getFreq(lst) 

code, tree = Huffman_code(freq) 

encoded = ''.join([code[t] for t in ro]) 
print('Encoded text:',encoded) 

w_file = open('encrypt.txt','wt') 
w_file.write(encoded) 
w_file.close() 

d_file = open('encrypt.txt', 'r') 

dec_ode = d_file.read() 

decoded = [] 
i = 0 
while i < len(dec_ode): # decoding using the binary graph 
    ch = dec_ode[i] 
    act = tree[ch] 
    while not isinstance(act, str): 
     i += 1 
     ch = dec_ode[i] 
     act = act[ch] 
    decoded.append(act) 
    i += 1 


test2_file = open('decode.txt', 'wt') 
test2_file.write(''.join(decoded)) 

test2_file.close() 

print('Decoded text:',''.join(decoded)) 

Answer 1

試試這個作爲你的getFreq函數：

def getFreq(mylst): 
    counters = [0 for _ in range(256)] 
    for c in mylst: 
     counters[ord(c)] += 1 
    return { chr(c): v for c, v in enumerate(counters) } 

您需要查看你的角色的列表以字節爲單位，而不是不同的字符。此函數將輸入字符轉換爲相應的ASCII值，並使用它來索引到計數器列表中。例如，每次遇到a時，counters的第97個元素都會增加。然後在所有字符被計數後counters被轉換回像你的程序預期的字典。