126 lines
4.6 KiB
Python
Executable File
126 lines
4.6 KiB
Python
Executable File
#!/usr/bin/env python
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import sys, os, string
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# Utility for handling the intermediate 'secondary memory'
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def touchopen(filename, *args, **kwargs):
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try:
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os.remove(filename)
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except OSError:
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pass
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open(filename, "a").close() # "touch" file
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return open(filename, *args, **kwargs)
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# The constrained memory should have no more than 1024 cells
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data = []
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# We're lucky:
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# The stop words are only 556 characters and the lines are all
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# less than 80 characters, so we can use that knowledge to
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# simplify the problem: we can have the stop words loaded in
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# memory while processing one line of the input at a time.
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# If these two assumptions didn't hold, the algorithm would
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# need to be changed considerably.
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# Overall strategy: (PART 1) read the input file, count the
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# words, increment/store counts in secondary memory (a file)
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# (PART 2) find the 25 most frequent words in secondary memory
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# PART 1:
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# - read the input file one line at a time
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# - filter the characters, normalize to lower case
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# - identify words, increment corresponding counts in file
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# Load the list of stop words
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f = open('../stop_words.txt')
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data = [f.read(1024).split(',')] # data[0] holds the stop words
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f.close()
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data.append([]) # data[1] is line (max 80 characters)
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data.append(None) # data[2] is index of the start_char of word
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data.append(0) # data[3] is index on characters, i = 0
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data.append(False) # data[4] is flag indicating if word was found
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data.append('') # data[5] is the word
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data.append('') # data[6] is word,NNNN
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data.append(0) # data[7] is frequency
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# Open the secondary memory
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word_freqs = touchopen('word_freqs', 'rb+')
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# Open the input file
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f = open(sys.argv[1], 'r')
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# Loop over input file's lines
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while True:
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data[1] = [f.readline()]
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if data[1] == ['']: # end of input file
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break
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if data[1][0][len(data[1][0])-1] != '\n': # If it does not end with \n
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data[1][0] = data[1][0] + '\n' # Add \n
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data[2] = None
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data[3] = 0
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# Loop over characters in the line
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for c in data[1][0]: # elimination of symbol c is exercise
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if data[2] == None:
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if c.isalnum():
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# We found the start of a word
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data[2] = data[3]
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else:
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if not c.isalnum():
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# We found the end of a word. Process it
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data[4] = False
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data[5] = data[1][0][data[2]:data[3]].lower()
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# Ignore words with len < 2, and stop words
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if len(data[5]) >= 2 and data[5] not in data[0]:
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# Let's see if it already exists
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while True:
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data[6] = str(word_freqs.readline().strip(), 'utf-8')
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if data[6] == '':
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break;
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data[7] = int(data[6].split(',')[1])
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# word, no white space
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data[6] = data[6].split(',')[0].strip()
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if data[5] == data[6]:
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data[7] += 1
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data[4] = True
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break
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if not data[4]:
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word_freqs.seek(0, 1) # Needed in Windows
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word_freqs.write(bytes("%20s,%04d\n" % (data[5], 1), 'utf-8'))
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else:
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word_freqs.seek(-26, 1)
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word_freqs.write(bytes("%20s,%04d\n" % (data[5], data[7]), 'utf-8'))
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word_freqs.seek(0,0)
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# Let's reset
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data[2] = None
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data[3] += 1
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# We're done with the input file
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f.close()
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word_freqs.flush()
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# PART 2
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# Now we need to find the 25 most frequently occurring words.
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# We don't need anything from the previous values in memory
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del data[:]
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# Let's use the first 25 entries for the top 25 words
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data = data + [[]]*(25 - len(data))
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data.append('') # data[25] is word,freq from file
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data.append(0) # data[26] is freq
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# Loop over secondary memory file
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while True:
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data[25] = str(word_freqs.readline().strip(), 'utf-8')
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if data[25] == '': # EOF
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break
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data[26] = int(data[25].split(',')[1]) # Read it as integer
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data[25] = data[25].split(',')[0].strip() # word
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# Check if this word has more counts than the ones in memory
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for i in range(25): # elimination of symbol i is exercise
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if data[i] == [] or data[i][1] < data[26]:
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data.insert(i, [data[25], data[26]])
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del data[26] # delete the last element
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break
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for tf in data[0:25]: # elimination of symbol tf is exercise
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if len(tf) == 2:
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print(tf[0], '-', tf[1])
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# We're done
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word_freqs.close()
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