Python基础(十二) 字典的使用
2015-11-05 11:21
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Python基础(十二) 字典的使用
字典的初始化和基本操作
初始化:phoneBook = {"Alice":"0458","Lily":"2548","Tom":"1786"} #用dict函数初始化 phoneBook = dict(Alice = "0458",Lily = '2548') #用dict函数和 (键,值) 初始化 items = [('Alice', '0458'),('Lily','2548')] phoneBook = dict(items)
基本操作:
#根据键查找相应值 print phoneBook['Lily'] #输出键值对的个数 print len(phoneBook) #修改某个键对应的值 phoneBook['Lily'] = '2579' print phoneBook['Lily'] #删除某个键值 del phoneBook['Lily'] print phoneBook print "Lily in phoneBook ? ","Lily" in phoneBook
字典常用函数
clear()
#clear()方法 清空字典中的所有项 dict_x = {} dict_x['name'] = "value" dict_y = dict_x dict_x = {} print "dict_x :",dict_x print "dict_y :",dict_y dict_x['name'] = "value" dict_y = dict_x dict_x.clear() print "dict_x :",dict_x print "dict_y :",dict_y
copy()
#copy() 方法 (浅拷贝) dict_x = {"name":"Lily","phoneNum":"2579","friends":["Lucy","Lilei"]} #字典y是x的一个浅拷贝 dict_y = dict_x.copy() #替换字典y 的 name值 原字典x的name值不会跟着改变 dict_y["name"] = "LilyChange" print r"dict_x[name] = ",dict_x["name"] print r"dict_y[name] = ",dict_y["name"] #修改字典y 的 friends值 原字典x的friends值会跟着改变 dict_y["friends"].remove("Lucy") print r"dict_x[friends] = ",dict_x["friends"] print r"dict_y[friends] = ",dict_y["friends"]
deepcopy(dict)
#deepcopy(dict) 方法 (深拷贝) from copy import deepcopy dict_x = {"name":"Lily","phoneNum":"2579","friends":["Lucy","Lilei"]} #字典y是x的一个浅拷贝 dict_y = deepcopy(dict_x) #替换字典y 的 name值 原字典x的name值不会跟着改变 dict_y["name"] = "LilyChange" print r"dict_x[name] = ",dict_x["name"] print r"dict_y[name] = ",dict_y["name"] #修改字典y 的 friends值 原字典x的friends值不会跟着改变 dict_y["friends"].remove("Lucy") print r"dict_x[friends] = ",dict_x["friends"] print r"dict_y[friends] = ",dict_y["friends"]
fromkeys(['key1','key2'])
#fromkeys(['key1','key2'])使用给定键建立新的字典 每个键值的默认值为None fromkeysdict = dict.fromkeys(['key1','key2']) print fromkeysdict
get('key')
#get('key') 方法如果key不在字典中 则返回None 而 dictname['key']如果没有对应key在字典中则会报错 getDic = {} #getDic["keyname"] #此句会报错 print getDic.get("keyname")
has_key('key')
#has_key('key') 检查字典中是否拥有某个key hasKeyDict = {"name":"Lily","age":12} print hasKeyDict.has_key("name") print hasKeyDict.has_key("grade")
items 和 iteritems
#items 方法将所有的字典项以列表的方式返回.这些列表项中的每一项都来自于(键,值) #但是项在返回时没有固定顺序 mDict = {"title":"MyDict","Context":"this is my Dict for Test ","Author":"Guodong"} myDictList = mDict.items() print myDictList[1]
keys 和 iterkeys
#keys 和 iterkeys #keys方法返回所有键的列表 #iterkeys方法返回键的迭代器 mDict = {"title":"MyDict","Context":"this is my Dict for keys ","Author":"Guodong"} print mDict.keys()
pop('key')
#pop方法移除对应键的键值对 mDict = {"title":"MyDict","Context":"this is my Dict for keys ","Author":"Guodong"} mDict.pop("title") print mDict
popitem()
#popitem 随机弹出列表的某一项 (一般会弹出第一项 但是Python不确定一定总是第一项) mDict = {"title":"MyDict","Context":"this is my Dict for keys ","Author":"Guodong"} mDict.popitem() print mDict
setdefault('key','value')
#setdefault 给键值设定一个初始值 d = {} #如果键不存在 会相应更新字典 d.setdefault('name',"none") print d d['name'] = "Lily" #如果键值已经存在 则不会改变原有值 d.setdefault('name',"none") print d
update(dict)
#update 通过另一个字典更新字典 d1 = {"name":"none","age":13} d2 = {"name":"guodong"} d1.update(d2) print d1
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