python学习笔记——列表

创建

>>> list = ["a", "b", "c", "d", "e"]

>>> list

['a', 'b', 'c', 'd', 'e']

获取某一元素或子串

>>> list = ["a", "b", "c", "d", "e"]

#取得第一个元素

>>> list[0]

'a'

 

# 取得最后一个元素

>>> list[-1]

'e'

# 若索引值超出列表长度之外，就会报错

>>> list[10]

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

IndexError: list index out of range

 

# 使用切片，模拟javascript的slice功能，获取子串

>>> list[1:4]

['b', 'c', 'd']

 

# 切片的起始索引默认为0

>>> list[:3]

['a', 'b', 'c']

 

# 切片的起始索引默认为-1

>>> list[3:]

['d', 'e']

 

# 超出范围会自动修正为列表的长度

>>> list[3:10]

['d', 'e']

替换

>>> list = ["a", "b", "c", "d", "e"]

 

# 替换单个元素

>>> list[3] = "D"

>>> list

['a', 'b', 'c', 'D', 'e']

 

# 替换N个元素

>>> list[:3] = ["A", "B", "C"]

>>> list

['A', 'B', 'C', 'D', e]

 

# 通换替换进行扩展，有点像javascript的splice

>>> list[-1:] = ["E", "F"]

>>> list

['A', 'B', 'C', 'D', 'E', 'F']

 

# 通换替换进行收缩

>>> list[-2:] = "E"

>>> list

['A', 'B', 'C', 'D', 'E']

追加

>>> list = ['b'] # push一个元素，注意此方法没有返回值 >>> list.append('e') >>> list >>> ['b', 'e'] # 在指定位置上添加元素 >>> list.insert(0, 'a') >>> list ['a', 'b', 'e'] # 在指定位置上添加多个无形 >>> list[2:2] = ['c', 'd'] >>> list ['a', 'b', 'c', 'd', 'e']

合并

>>> list1 = ['a', 'b', 'c']

>>> list2 = ['d', 'e']

 

#  使用+号操作符生成一个全新的列表

>>> list3 = list1 + list2

>>> list3

['a', 'b', 'c', 'd', 'e']

>>> list1

['a', 'b', 'c']

 

# 使用extend在原列表上进行扩展，注意此方法没有返回值

>>> list1.extend(list2)

>>> list1

['a', 'b', 'c', 'd', 'e']

检测

>>> list = ["a", "b", "c", "a", "b"]

 

# 判定其是否为目标列表的成员

>>> "b" in list

True

>>> "e" in list

False

 

# 使用index方法还可以取得其在列表的位置

>>> list.index("a")

0

 

# 但是找不到时会报错，shit，什么破设计

>>> list.index("e")

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

ValueError: list.index(x): x not in list

</module>

删除

>>> list = ['a', 'a', 'a', 'b', 'b', 'b', 'c', 'c', 'c']

 

# 类似javascript的pop函数

>>> list.pop()

'b'

>>> list

['a', 'a', 'a', 'b', 'b', 'b', 'c', 'c']

 

# 可以通过传参，实现javascript的shift功能

>>> list.pop(0)

'a'

>>> list

['a', 'a', 'b', 'b', 'b', 'c', 'c']

 

# 指定移除的元素，每次只移除1个

>>> list.remove('b')

>>> list

['a', 'a', 'b', 'b', 'c', 'c']

 

# 但如果不存在就会报错，这个非常不人性化

>>> list.remove(10)

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

ValueError: list.remove(x): x not in list

 

# 清空所有‘b’元素

>>> while 'b' in list: list.remove('b')

...

>>> list

['a', 'a', 'c', 'c']

 

# 移除一组元素

>>> del list[1:3] #与 list[1:3] = [] 相同

>>> list

['a', 'c']

 

# 全部清空

>>> del list[:] #与 list[:] = [] 相同

>>> list

[]

</module>

统计

>>> list = ['a', 'a', 'b', 'c']

 

>>> len(list)

4

 

# 返回a在列表出现的次数

>>> list.count('a')

2

列表解析

>>> S = [x**2 for x in range(10)]

>>> V = [2**i for i in range(13)]

>>> M = [x for x in S if x % 2 == 0]

>>>

>>> print S; print V; print M

[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

[1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096]

[0, 4, 16, 36, 64]

>>> noprimes = [j for i in range(2, 8) for j in range(i*2, 50, i)]

>>> primes = [x for x in range(2, 50) if x not in noprimes]

>>> print primes

[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47]

>>> words = 'The quick brown fox jumps over the lazy dog'.split()

>>> print words

['The', 'quick', 'brown', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']

>>>

>>> stuff = [[w.upper(), w.lower(), len(w)] for w in words]

>>> for i in stuff:

...     print i

...

['THE', 'the', 3]

['QUICK', 'quick', 5]

['BROWN', 'brown', 5]

['FOX', 'fox', 3]

['JUMPS', 'jumps', 5]

['OVER', 'over', 4]

['THE', 'the', 3]

['LAZY', 'lazy', 4]

['DOG', 'dog', 3]

>>>

>>> stuff = map(lambda w: [w.upper(), w.lower(), len(w)], words)

>>> for i in stuff:

...     print i

...

['THE', 'the', 3]

['QUICK', 'quick', 5]

['BROWN', 'brown', 5]

['FOX', 'fox', 3]

['JUMPS', 'jumps', 5]

['OVER', 'over', 4]

['THE', 'the', 3]

['LAZY', 'lazy', 4]

['DOG', 'dog', 3]

将一个二维列表平坦化

>>> list = [[1, 3, 5], [2, 4]]

>>> [flatten for inner in list for flatten in inner]

[1, 3, 5, 2, 4]

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