TypeError: list indices must be integers, not str
故字典是python中唯一的映射类型,key-value(哈希表),字典对象是可变的,但key必须用不可变对象。 2.字典的定义 对字典的处理方法 In [6]: dic. dic.clear dic.items dic.pop dic.viewitems dic.copy dic.iteritems dic.popitem dic.viewkeys dic.fromkeys dic.iterkeys dic.setdefault dic.viewvalues dic.get dic.itervalues dic.update dic.has_key dic.keys dic.values • 简单字典创建 In [10]: dic = { "name":"lee","age":"10","class":"math" } In [11]: dic["name"] Out[11]: 'lee' In [12]: dic['class'] Out[12]: 'math' In [13]: dic[1] ##不能用这种方法索引 --------------------------------------------------------------------------- KeyError Traceback (most recent call last) <ipython-input-13-3e9497c0fbd7> in <module>() ----> 1 dic[1]
KeyError: 1
• 内建方法:fromkeys 字典中的key有相同的value值,默认为None In [14]: di = {}.fromkeys(('username','password'),'fentiao') In [15]: di Out[15]: {'password': 'fentiao', 'username': 'fentiao'} In [16]: di1 = {}.fromkeys(('username','password'),) In [17]: di1
Out[17]: {'password': None, 'username': None}
In [32]: dic.fromkeys([1,2,3,4]) Out[32]: {1: None, 2: None, 3: None, 4: None} In [33]: dic.fromkeys([1,2,3,4],'hello') Out[33]: {1: 'hello', 2: 'hello', 3: 'hello', 4: 'hello'} 3.字典值的访问 •直接通过key访问 In [18]: dic Out[18]: {'age': '10', 'class': 'math', 'name': 'lee'} In [19]: dic['name'] Out[19]: 'lee' In [20]: dic['class'] Out[20]: 'math' In [21]: dic['age'] Out[21]: '10' •循环遍历访问 In [22]: dic Out[22]: {'age': '10', 'class': 'math', 'name': 'lee'} In [23]: for key in dic: ....: print dic[key] ....: 10 lee
math
In [34]: dic Out[34]: {'age': '10', 'class': 'math', 'name': 'lee'} In [35]: for key in dic.keys(): ....: print "key=%s" % key ....: key=age key=name key=class In [36]: for value in dic.values(): print "value=%s" % value ....: value=10 value=lee value=math 4.字典key-value的添加 •dic[key] = value In [24]: dic['kind'] = 'cat' In [25]: dic
Out[25]: {'age': '10', 'class': 'math', 'kind': 'cat', 'name': 'lee'}//通过这个操作,我们会发现字典是无序的数据类型
5.字典的更新 1) In [4]: dic = { "name":"lee","age":"10","class":"math" } In [5]: dic1 = {"gender":"male"} In [6]: dic.update(dic1) In [7]: dic
Out[7]: {'age': '10', 'class': 'math', 'gender': 'male', 'name': 'lee'}
2) In [8]: dic = {"home":"456","hello":"123"} In [9]: dic1 = {"sisi":"123","home":"123"} In [10]: dic.update(dic dic dic1 dict In [10]: dic.update(dic1) In [11]: dic Out[11]: {'hello': '123', 'home': '123', 'sisi': '123'} 6.字典的删除 •dic.clear() //删除字典中的所有元素 In [11]: dic Out[11]: {'hello': '123', 'home': '123', 'sisi': '123'} In [12]: dic.c dic.clear dic.copy In [12]: dic.clear() In [13]: dic
Out[13]: {}
•del(dic) //删除字典本身字典的常用方法 In [14]: dic1 Out[14]: {'home': '123', 'sisi': '123'} In [15]: del(dic1) In [16]: dic1 --------------------------------------------------------------------------- NameError Traceback (most recent call last) <ipython-input-16-c95a6e8d4d0a> in <module>() ----> 1 dic1
NameError: name 'dic1' is not defined
• dic.pop(key) //根据key值删除字典的元素; In [19]: dic = { "name":"lee","age":"10","class":"math" } In [21]: dic.pop("age") Out[21]: '10' In [22]: dic Out[22]: {'class': 'math', 'name': 'lee'} • dic.popitem() //随机删除字典元素,返回(key,value) In [22]: dic
Out[22]: {'class': 'math', 'name': 'lee'}
In [23]: dic.popitem() Out[23]: ('name', 'lee') In [24]: dic
Out[24]: {'class': 'math'}
• dic.keys() //返回字典的所有key值 In [25]: dic = { "name":"lee","age":"10","class":"math" } In [26]: dic Out[26]: {'age': '10', 'class': 'math', 'name': 'lee'} In [27]: dic.keys() Out[27]: ['age', 'name', 'class'] In [28]: dic.values() Out[28]: ['10', 'lee', 'math'] • dict.get() //如果key存在于字典中,返回对应value值 In [29]: dic.get("age")
Out[29]: '10'
•dict.has_keys() //字典中是否存在某个key值 In [30]: dic.has_key("age") Out[30]: True In [31]: dic.has_key("dddd")
Out[31]: False
7. In [11]: dic Out[11]: {'age': '10', 'class': 'math', 'name': 'lee'} In [12]: for k,v in dic.items(): ....: print "%s -> %s" %(k,v) ....: age -> 10 name -> lee class -> math 8.小总结 此处的有序无序是指内部的存放顺序与元素的放入顺序是否有关 字符串： 书写方式：'' "" """ """ ''' ''' 不可变数据类型 有序 列表： 书写方式：[] 可变数据类型 有序序列 元组： 书写方式：() 不可变数据类型 有序序列 集合： 书写方式：{1,2} 可变数据类型 无序 字典： 书写方式：{"name":"hello"} 可变数据类型 无序 9.列表的应用 In [14]: data = ['fentiao','50','1000',(2017,12,3)] In [15]: name, shares, juankuan, date = data In [16]: print name,shares, juankuan, date fentiao 50 1000 (2017, 12, 3) In [18]: print name,juankuan fentiao 1000 In [19]: _,shares, _,date = data In [20]: print shares,date 50 (2017, 12, 3) In [21]: 对一组数据去掉最大和i最小值然后求平均值 In [25]: import heapq In [26]: li = [90,91,97,99,94,95] In [27]: print heapq.nlargest(1,li) [99] In [28]: li.sort() //先排序 In [29]: li Out[29]: [90, 91, 94, 95, 97, 99] In [30]: li.pop(0) //删除最小值 Out[30]: 90 In [31]: li.pop(len(li)-1) //删除最大值 Out[31]: 99 In [32]: sum(li)/len(li) //求平均值 Out[32]: 94
In [33]:
10.用字典写四则运算 #!/usr/bin/env python # coding:utf-8 from __future__ import division ''' @author:houruiyun @file:2.py @contact:674211605.qq.com @time:6/25/172:45 AM @desc: ''' num1 = input('input num1:') oper = raw_input('act:') num2 = input('input num2:') dic = {'+':num1+num2, '-':num1-num2, '*':num1*num2, '/':num1/num2} if oper in dic.keys(): print dic[oper]
