Introducing Python Lists

Python List 对象是最常用的序列类型，其值可以包含多种类型，是可变的，有序的序列。
下面来通过实例学习一下 Python 内置的 Lists 类型，及其常用操作符、表达式等。

Operators

$ python
Python 2.7.5 (default, Aug 25 2013, 00:04:04)
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.0.68)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
# 空 list
>>> empty_list = []
>>> empty_list
[]

# 非空 list
>>> colors = ["red", "yellow", "blue"]
>>> colors
['red', 'yellow', 'blue']

# 计算长度
>>> len(colors)
3

# 索引操作
>>> colors[0]
'red'
>>> colors[-1]
'blue'
>>> colors[0:2]
['red', 'yellow']
>>> colors[0] = 'black'
>>> colors
['black', 'yellow', 'blue']

# 合并
>>> colors + ['white']
['black', 'yellow', 'blue', 'white']

Methods

>>> colors
['black', 'yellow', 'blue']

# 追加 value
>>> colors.append('white')
>>> colors
['black', 'yellow', 'blue', 'white']

# 计算 value 出现次数
>>> colors.count('red')
0
>>> colors.count('black')
1

# 扩展 list
>>> colors.extend(['gray'])
>>> colors
['black', 'yellow', 'blue', 'white', 'gray']

# 计算 index 索引
>>> colors.index('blue')
2

# 插入数据到指定 index
>>> colors.insert(0, 'red')
>>> colors
['red', 'black', 'yellow', 'blue', 'white', 'gray']

# 取出数据
>>> colors.pop()
'gray'
>>> colors
['red', 'black', 'yellow', 'blue', 'white']
>>> colors.pop(1)
'black'
>>> colors
['red', 'yellow', 'blue', 'white']

# 删除数据
>>> colors.remove('white')
>>> colors
['red', 'yellow', 'blue']

# 排序
>>> colors.sort()
>>> colors
['blue', 'red', 'yellow']

# 倒序
>>> colors.reverse()
>>> colors
['yellow', 'red', 'blue']

List in Action

下面记录了 Python List 的一些实用操作。请看示例：

# iterate list
colors = ["red", "yellow", "blue"]
>>> for color in colors:
...   print color
...
red
yellow
blue

# iterate list with index
>>> for index, color in enumerate(colors):
...   print color, index
...
red 0
yellow 1
blue 2

# 合并为字符串
>>> ','.join(colors)
'red,yellow,blue'

# change sort order
>>> colors.sort(key=str.lower)
>>> colors
['blue', 'red', 'yellow']
>>> colors.sort(key=str.lower, reverse=True)
>>> colors
['yellow', 'red', 'blue']

# change integer list join to string
>>> list_demo = [1, 2, 3, 4]
>>> '_'.join([str(i) for i in list_demo])
"1_2_3_4"

2014-05-14