关于Python的列表和元组

python的列表和元组

基本概念

list：可以放置任意数据类型的动态的元素指向可变的有序集合，创建之后可以随意增删改元素。
tuple：可以放置任意数据类型的静态的元素指向不可变的有序集合，创建之后无法增删改元素。
主要区别：动态还是静态，元素指向可变还是不可变！

list01 = [1,2,3,4]
list01[3] = 444
list01
tuple01 = (1,2,3,4)
tuple01[3] = 444
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-5-3781e7f64cf2> in <module>()
      5 list01
      6 tuple01 = (1,2,3,4)
----> 7 tuple01[3] = 444

TypeError: 'tuple' object does not support item assignment
对一个tuple进行这种操作直接报错！

基本操作

list

创建list

使用[]和函数list()都可以创建列表，但是[]更高效！
import timeit
print(timeit.timeit("[x for x in range(0,10000)]", number=10000))
print(timeit.timeit("list(x for x in range(0,10000))", number=10000))
3.7451904740009923
7.075908677012194

将其他数据类型转换成list

print(timeit.timeit("a_tuple = ('ready','fire','pool');[a_tuple]", number=10000))
print(timeit.timeit("a_tuple = ('ready','fire','pool');list(a_tuple)", number=10000))
感觉还是用[]更高效！
0.0006942460022401065
0.0024700629874132574

list的切片操作

citys = ["BeiJing","NewYork","Singapore","Toronto"]
citys[0] = "Shanghai"
new_citys = citys
print(new_citys[0:2])
print(new_citys[:])
print(new_citys[:2])
print(new_citys[0:3:2])
print(new_citys[-1])

['Shanghai', 'NewYork']
['Shanghai', 'NewYork', 'Singapore', 'Toronto']
['Shanghai', 'NewYork']
['Shanghai', 'Singapore']
Toronto
list和tuple都支持切片操作和负数索引！

list的常用操作

#append在末尾添加元素
new_citys.append("Beijing")
print(new_citys)
#合并list
import timeit
print(timeit.timeit("list001=[];list001.extend([x for x in range(1,100000)])",number=1000))
print(timeit.timeit("list001=[];list001+[x for x in range(1,100000)]", number=1000))
['Shanghai', 'NewYork', 'Singapore', 'Toronto', 'Beijing']
4.620128600974567
4.220356322999578

#insert在指定位置插入元素
citys = ["BeiJing","NewYork","Singapore","Toronto"]
citys.insert(0,"Tokyo")
print(citys)
#del删除元素
del citys[0]
print(citys)
#remove删除元素
citys.remove("Toronto")
print(citys)
#pop删除元素
citys.pop()
print(citys)
['Tokyo', 'BeiJing', 'NewYork', 'Singapore', 'Toronto']
['BeiJing', 'NewYork', 'Singapore', 'Toronto']
['BeiJing', 'NewYork', 'Singapore']
['BeiJing', 'NewYork']

用append把元素添加到尾部，用pop从尾部删除元素这种后进先出的数据结构叫栈stack。
用append把元素添加到尾部，用pop(0)从首部删除元素这种后进后出的数据结构叫队列。

#使用index查询特定值的位置
citys = ["BeiJing","NewYork","Singapore","Toronto"]
citys.index("NewYork")
#使用in判断元素是否存在
print(citys)
'Tokyo' in citys
#使用count记录特定值出现的次数
citys.append("Toyko");citys.append("Toyko")
citys.count("Toyko")
['BeiJing', 'NewYork', 'Singapore', 'Toronto']
2

list和tuple常用的内置函数

list001 = [3,".",1,4,1,5,9,2,6,5,3,5,8,9,8]
print(list001.count(5))
print(list001.index(8))
list001.reverse()
print(list001)
list001_new=[x for x in list001 if type(x) != str];print(list001_new);list001_new.reverse();print(list001_new)
3
12
[8, 9, 8, 5, 3, 5, 6, 2, 9, 5, 1, 4, 1, '.', 3]
[8, 9, 8, 5, 3, 5, 6, 2, 9, 5, 1, 4, 1, 3]
[3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 8]

tuple001 = (3,".",1,4,1,5,9,2,6,5,3,5,8,9,8)
print(tuple001.count(5))
print(tuple001.index(8))
print(list(reversed(tuple001)))
tuple001_new=sorted(tuple(x for x in tuple001 if type(x) != str));print(tuple001_new)
3
12
[8, 9, 8, 5, 3, 5, 6, 2, 9, 5, 1, 4, 1, '.', 3]
[1, 1, 2, 3, 3, 4, 5, 5, 5, 6, 8, 8, 9, 9]

count(item)统计list或tuple中item出现的次数。
index(item)返回list或tuple中item第一次出现的索引。
list.reverse()原地倒转list，tuple没有这个函数。
list.sort()排序list，tuple没有这个函数。
reversed()对list或tuple进行倒转，返回一个处理好的新的list或tuple。
sorted()对list或tuple进行排序，返回一个处理好的新的list或tuple。

list和tuple的存储差异

print(list().__sizeof__())
print(tuple().__sizeof__())
print(list(x for x in range(0,10000)).__sizeof__())
print(tuple(x for x in range(0,10000)).__sizeof__())
print(list(x for x in range(0,100000)).__sizeof__())
print(tuple(x for x in range(0,100000)).__sizeof__())
print(list(x for x in range(0,1000000)).__sizeof__())
print(tuple(x for x in range(0,1000000)).__sizeof__())
40
24
83088
80024
879816
800024
8250144
8000024
由此可见动态的可变的list占用的空间更多！

list和tuple的性能

#初始化相同元素tuple更快
import timeit
print(timeit.timeit("[1,2,3,4,5,6,7,8,9,10]", number=1000000))
print(timeit.timeit("(1,2,3,4,5,6,7,8,9,10)", number=1000000))
0.11689231399213895
0.014740854036062956
#索引操作基本
import timeit
print(timeit.timeit("a=[1,2,3,4,5,6,7,8,9,10];b=a[9]", number=1000000))
print(timeit.timeit("a=(1,2,3,4,5,6,7,8,9,10);b=a[9]", number=1000000))
0.14129851799225435
0.03787975601153448

总结

tuple相比list更加轻量化，性能稍优，但是增删改list更优！