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POHuffman encoding: how to write binary data in Python
 

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    <p>I have tried methods using the struct module, as shown by the lines commented out in my code, but it didn't work out. Basically I have two options: I can either write the binary data code by code (my code are sequences of bits of length varying from 3 to 13 bits), or convert the whole string of n characters (n=25000+ in this case) to binary data. But I don't know how to implement either methods. Code:</p> <pre><code>import heapq import binascii import struct def createFrequencyTupleList(inputFile): frequencyDic = {} intputFile = open(inputFile, 'r') for line in intputFile: for char in line: if char in frequencyDic.keys(): frequencyDic[char] += 1 else: frequencyDic[char] = 1 intputFile.close() tupleList = [] for myKey in frequencyDic: tupleList.append((frequencyDic[myKey],myKey)) return tupleList def createHuffmanTree(frequencyList): heapq.heapify(frequencyList) n = len(frequencyList) for i in range(1,n): left = heapq.heappop(frequencyList) right = heapq.heappop(frequencyList) newNode = (left[0] + right[0], left, right) heapq.heappush(frequencyList, newNode) return frequencyList[0] def printHuffmanTree(myTree, someCode,prefix=''): if len(myTree) == 2: someCode.append((myTree[1] + "@" + prefix)) else: printHuffmanTree(myTree[1], someCode,prefix + '0') printHuffmanTree(myTree[2], someCode,prefix + '1') def parseCode(char, myCode): for k in myCode: if char == k[0]: return k[2:] if __name__ == '__main__': myList = createFrequencyTupleList('input') myHTree = createHuffmanTree(myList) myCode = [] printHuffmanTree(myHTree, myCode) inputFile = open('input', 'r') outputFile = open('encoded_file2', "w+b") asciiString = '' n=0 for line in inputFile: for char in line: #outputFile.write(parseCode(char, myCode)) asciiString += parseCode(char, myCode) n += len(parseCode(char, myCode)) #values = asciiString #print n #s = struct.Struct('25216s') #packed_data = s.pack(values) #print packed_data inputFile.close() #outputFile.write(packed_data) outputFile.close() </code></pre>
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