Python list操作用法总结

本文实例讲述了Python list操作用法。分享给大家供大家参考，具体如下：

List是python中的基本数据结构之一，和Java中的ArrayList有些类似，支持动态的元素的增加。list还支持不同类型的元素在一个列表中，List is an Object。

最基本的创建一个列表的方法

复制代码 代码如下:

myList = ['a','b','c']

Python list常见操作如下：

创建列表

复制代码 代码如下:

sample_list = ['a',1,('a','b')]

Python 列表操作

复制代码 代码如下:

sample_list = ['a','b',0,1,3]

得到列表中的某一个值

value_start = sample_list[0]
end_value = sample_list[-1]

删除列表的第一个值

复制代码 代码如下:

del sample_list[0]

在列表中插入一个值

复制代码 代码如下:

sample_list[0:0] = ['sample value']

得到列表的长度

复制代码 代码如下:

list_length = len(sample_list)

列表遍历

for element in sample_list:
  print(element)

Python 列表高级操作/技巧

产生一个数值递增列表

num_inc_list = range(30)
#will return a list [0,1,2,...,29]

用某个固定值初始化列表

initial_value = 0
list_length = 5
sample_list = [ initial_value for i in range(10)]
sample_list = [initial_value]*list_length
# sample_list ==[0,0,0,0,0]

附：python内置类型

1、list：列表（即动态数组，C++标准库的vector，但可含不同类型的元素于一个list中）

复制代码 代码如下:

a = ["I","you","he","she"] #元素可为任何类型。

下标：按下标读写，就当作数组处理
以0开始，有负下标的使用
0第一个元素，-1最后一个元素，
-len第一个元 素，len-1最后一个元素

取list的元素数量

len(list) #list的长度。实际该方法是调用了此对象的__len__(self)方法。

创建连续的list

L = range(1,5)   #即 L=[1,2,3,4],不含最后一个元素
L = range(1, 10, 2) #即 L=[1, 3, 5, 7, 9]

list的方法

L.append(var)  #追加元素
L.insert(index,var)
L.pop(var)   #返回最后一个元素，并从list中删除之
L.remove(var)  #删除第一次出现的该元素
L.count(var)  #该元素在列表中出现的个数
L.index(var)  #该元素的位置,无则抛异常
L.extend(list) #追加list，即合并list到L上
L.sort()    #排序
L.reverse()   #倒序
list 操作符:,+,*，关键字del
a[1:]    #片段操作符，用于子list的提取
[1,2]+[3,4] #为[1,2,3,4]。同extend()
[2]*4    #为[2,2,2,2]
del L[1]  #删除指定下标的元素
del L[1:3] #删除指定下标范围的元素

list的复制

L1 = L   #L1为L的别名，用C来说就是指针地址相同，对L1操作即对L操作。函数参数就是这样传递的
L1 = L[:]  #L1为L的克隆，即另一个拷贝。

复制代码 代码如下:

list comprehension
[ for k in L if ]

2、dictionary： 字典（即C++标准库的map）

复制代码 代码如下:

dict = {'ob1':'computer', 'ob2':'mouse', 'ob3':'printer'}

每一个元素是pair，包含key、value两部分。key是Integer或string类型，value 是任意类型。

键是唯一的，字典只认最后一个赋的键值。

dictionary的方法

D.get(key, 0)    #同dict[key]，多了个没有则返回缺省值，0。[]没有则抛异常
D.has_key(key)   #有该键返回TRUE，否则FALSE
D.keys()      #返回字典键的列表
D.values()
D.items()
D.update(dict2)   #增加合并字典
D.popitem()     #得到一个pair，并从字典中删除它。已空则抛异常
D.clear()      #清空字典，同del dict
D.copy()      #拷贝字典
D.cmp(dict1,dict2) #比较字典，(优先级为元素个数、键大小、键值大小)
          #第一个大返回1，小返回-1，一样返回0

dictionary的复制

dict1 = dict    #别名
dict2=dict.copy()  #克隆，即另一个拷贝。

3、tuple：元组（即常量数组）

复制代码 代码如下:

tuple = ('a', 'b', 'c', 'd', 'e')

可以用list的 [],:操作符提取元素。就是不能直接修改元素。

4、string： 字符串（即不能修改的字符list）

复制代码 代码如下:

str = "Hello My friend"

字符串是一个整 体。如果你想直接修改字符串的某一部分，是不可能的。但我们能够读出字符串的某一部分。

子字符串的提取

复制代码 代码如下:

str[:6]

字符串包含 判断操作符：in，not in
"He" in str
"she" not in str

string模块，还提供了很多方法，如

S.find(substring, [start [,end]]) #可指范围查找子串，返回索引值，否则返回-1
S.rfind(substring,[start [,end]]) #反向查找
S.index(substring,[start [,end]]) #同find，只是找不到产生ValueError异常
S.rindex(substring,[start [,end]])#同上反向查找
S.count(substring,[start [,end]]) #返回找到子串的个数
S.lowercase()
S.capitalize()   #首字母大写
S.lower()      #转小写
S.upper()      #转大写
S.swapcase()    #大小写互换
S.split(str, ' ')  #将string转list，以空格切分
S.join(list, ' ')  #将list转string，以空格连接

处理字符串的内置函数

len(str)        #串长度
cmp("my friend", str)  #字符串比较。第一个大，返回1
max('abcxyz')      #寻找字符串中最大的字符
min('abcxyz')      #寻找字符串中最小的字符

string的转换

oat(str) #变成浮点数，float("1e-1") 结果为0.1
int(str)    #变成整型， int("12") 结果为12
int(str,base)  #变成base进制整型数，int("11",2) 结果为2
long(str)    #变成长整型，
long(str,base) #变成base进制长整型，

字符串的格式化（注意其转义字符，大多如C语言的，略）

str_format % (参数列表) #参数列表是以tuple的形式定义的，即不可运行中改变

复制代码 代码如下:

>>>print ""%s's height is %dcm" % ("My brother", 180)
#结果显示为 My brother's height is 180cm

list 和 tuple 的相互转化

tuple(ls)
list(ls)

补充：

在python中list也是对象，所以他也有方法和属性，在ptython解释器中 使用help(list)可以查看其文档，部分开放方法如下：

这里以一个实例代码介绍这些方法的具体用法：

# coding=utf-8
# Filename : list.py
# Date: 2012 11 20
# 创建一个list方式
heatList = ['wade','james','bosh','haslem']
tableList = list('123') #list方法接受一个iterable的参数
print 'Miami heat has ',len(heatList),' NBA Stars , they are:'
#遍历list中的元素
for player in heatList:
  print player,
#向list添加元素
heatList.append('allen') #方式一：向list结尾添加 参数object
print '\nAfter allen join the team ,they are: '
print heatList
heatList.insert(4,'lewis') #方式二：插入一个元素 参数一：index位置 参数二：object
print 'After lewis join the team, they are:'
print heatList
heatList.extend(tableList) #方式三：扩展列表，参数：iterable参数
print 'After extend a table list,now they are :'
print heatList
#从list删除元素
heatList.remove('1')  #删除方式一：参数object 如有重复元素，只会删除最靠前的
print" Remove '1' ..now '1' is gone\n",heatList
heatList.pop()  #删除方式二：pop 可选参数index删除指定位置的元素 默认为最后一个元素
print "Pop the last element '3'\n",heatList
del heatList[6] #删除方式三：可以删除制定元素或者列表切片
print "del '3' at the index 6\n",heatList
#逻辑判断
#统计方法 count 参数：具体元素的值
print 'james apears ',heatList.count('wade'),' times'
#in 和 not in
print 'wade in list ? ',('wade' in heatList)
print 'wade not in list ? ',('wade' not in heatList)
#定位 index方法：参数：具体元素的值 可选参数：切片范围
print 'allen in the list ? ',heatList.index('allen')
#下一行代码会报错，因为allen不在前三名里
#print 'allen in the fisrt 3 player ? ',heatList.index('allen',0,3)
#排序和反转代码
print 'When the list is reversed : '
heatList.reverse()
print heatList
print 'When the list is sorted: '
heatList.sort() #sort有三个默认参数 cmp=None,key=None,reverse=False 因此可以制定排序参数以后再讲
print heatList
#list 的分片[start:end] 分片中不包含end位置的元素
print 'elements from 2nd to 3rd ' , heatList[1:3]

希望本文所述对大家Python程序设计有所帮助。

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