python常用字典操作范例详解编程语言

# experimenting with the Python dictionary 

# a seemingly unordered set of key:value pairs, types can be mixed 

# Python23 tested vegaseat 13feb2005 

# initialize a dictionary, here a dictionary of roman numerals 

romanD = {I:1,II:2,III:3,IV:4,V:5,VI:6,VII:7,VIII:8,IX:9} 

print "A dictionary is an unordered set of key:value pairs:" 

print romanD 

# create an empty dictionary 

D1 = {} 

# show empty dictionary contents and length (number of item/pairs) 

print "Empty Dictionary contains:" 

# shows {} 

print D1 

# shows Length = 0 

print "Length = ", len(D1) 

# add/load new key:value pairs by using indexing and assignment 

# here eins is the key, one is the key value 

# the start of a german to english dictionary 

D1[null] = zero 

D1[eins] = one 

D1[zwei] = two 

D1[drei] = three 

D1[vier] = four 

# print loaded dictionary and length 

# the dictionary key order allows for most efficient searching 

print "Dictionary now contains (notice the seemingly random order of pairs):" 

print D1 

print "Length = ",len(D1) 

# find the value by key (does not change dictionary) 

print "The english word for drei is ", D1[drei] 

# better 

if drei in D1: 

 print "The english word for drei is ", D1[drei] 

# create a list of the values in the dictionary 

L1 = D1.values() 

# the list can be sorted, the dictionary itself cannot 

L1.sort() 

print "A list of values in the dictionary (sorted):" 

print L1 

# create a list of dictionary keys 

L2 = D1.keys() 

L2.sort() 

print "A list of the dictionary keys (sorted):" 

print L2 

# does the dictionary contain a certain key? 

if D1.has_key(null): 

 print "Key null found!" 

else: 

 print "Key null not found!" 

# copy dictionary D1 to D2 (the order may not be the same) 

D2 = D1.copy() 

print "Dictionary D1 has been copied to D2:" 

print D2 

# delete an entry 

del D2[zwei] 

print "Dictionary D2 after zwei has been deleted:" 

print D2 

# extract the value and remove the entry 

# pop() changes the dictionary, use e3 = D2[drei] for no change 

e3 = D2.pop(drei) 

print "Extract value for key = drei and delete item from dictionary:" 

print e3 

print "Dictionary D2 after drei has been popped:" 

print D2 

print 

str1 = "I still miss you baby, but my aims gettin better!" 

print str1 

print "Count the characters in the above string:" 

# create an empty dictionary 

charCount = {} 

for char in str1: 

 charCount[char] = charCount.get(char, 0) + 1 

print charCount 

print 

if t in charCount: 

 print "There are %d t in the string" % charCount[t] 

print 

str2 = "It has been a rough day. I got up this morning put on a shirt and a" 

str2 = str2 + " button fell off. I picked up my briefcase and the handle came off." 

str2 = str2 + " Now I am afraid to go to the bathroom." 

print str2 

print "Count the words in the above string, all words lower case:" 

# create a list of the words 

wordList = str2.split(None) 

# create an empty dictionary 

wordCount = {} 

for word in wordList: 

 # convert to all lower case 

 word = word.lower() 

 # strip off any trailing period, if needed do other punctuations 

 if . in word: 

 word = word.rstrip(.) 

 # load key:value pairs by using indexing and assignment 

 wordCount[word] = wordCount.get(word, 0) + 1 

print wordCount 

print 

# put keys into list and sort 

keyList = wordCount.keys() 

keyList.sort() 

# display words and associated count in alphabetical order 

for keyword in keyList: 

 print keyword, "=", wordCount[keyword] 

# put the dictionary pairs into a list, use the romanD dictionary 

romanList = [] 

for key, value in romanD.items(): 

 # put value first for a meaningful sort 

 romanList.append((value, key)) 

romanList.sort() 

print "/nThe roman numeral dictionary put into a (value,pair) list then sorted:" 

print romanList 

print "/nList them as pairs on a line:" 

for i in xrange(len(romanList)): 

 print romanList[i][0],=, romanList[i][1] 

print 

# split the romanD dictionary into two lists 

print "Splitting the romanD dictionary into two lists:" 

romankeyList = [] 

romanvalueList = [] 

for key, value in romanD.items(): 

 romankeyList.append(key) 

 romanvalueList.append(value) 

print "Key List:",romankeyList 

print "Value List:",romanvalueList 

print 

# make a dictionary from the two lists 

print "Combining the two lists into a dictionary:" 

romanD1 = dict(zip(romankeyList, romanvalueList)) 

print romanD1 

# to save a Python object like a dictionary to a file 

# and load it back intact you have to use the pickle module 

import pickle 

print "The original dictionary:" 

print romanD1 

file = open("roman1.dat", "w") 

pickle.dump(romanD1, file) 

file.close() 

file = open("roman1.dat", "r") 

romanD2 = pickle.load(file) 

file.close() 

print "Dictionary after pickle.dump() and pickle.load():" 

print romanD2 

print 

# lets get rid of some duplicate words 

str = "Senator Strom Thurmond dressed as as Tarzan" 

print "/nOriginal string:" 

print str 

print "A list of the words in the string:" 

wrdList1 = str.split() 

print wrdList1 

def uniqueList(anyList): 

 """given a list, returns a unique list with the order retained""" 

 # create an empty dictionary 

 dic1 = {} 

 # use a list comprehension statement and the unique feature of a dictionary 

 return [dic1.setdefault(e,e) for e in anyList if e not in dic1] 

# a call to the above function will retain the order of words 

wrdList2 = uniqueList(wrdList1) 

print "Convert unique list back to string (order retained):" 

print " ".join(wrdList2)

原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/8187.html