python统计文本字符串里单词出现频率的方法

# word frequency in a text
# tested with Python24  vegaseat  25aug2005
# Chinese wisdom ...
str1 = """Man who run in front of car, get tired.
Man who run behind car, get exhausted."""
print "Original string:"
print str1
print
# create a list of words separated at whitespaces
wordList1 = str1.split(None)
# strip any punctuation marks and build modified word list
# start with an empty list
wordList2 = []
for word1 in wordList1:
  # last character of each word
  lastchar = word1[-1:]
  # use a list of punctuation marks
  if lastchar in [",", ".", "!", "?", ";"]:
    word2 = word1.rstrip(lastchar)
  else:
    word2 = word1
  # build a wordList of lower case modified words
  wordList2.append(word2.lower())
print "Word list created from modified string:"
print wordList2
print
# create a wordfrequency dictionary
# start with an empty dictionary
freqD2 = {}
for word2 in wordList2:
  freqD2[word2] = freqD2.get(word2, 0) + 1
# create a list of keys and sort the list
# all words are lower case already
keyList = freqD2.keys()
keyList.sort()
print "Frequency of each word in the word list (sorted):"
for key2 in keyList:
 print "%-10s %d" % (key2, freqD2[key2])