将数字应用于字符串的序列生成答案

【问题标题】：Sequence Generation with Number applied to string将数字应用于字符串的序列生成
【发布时间】：2013-06-21 16:56:29
【问题描述】：

我已经尝试过像 Lambda、列表理解和其他的序列生成器，但似乎我无法得到我真正想要的东西。我的最终目标是从 string[1:3]

之类的字符串中打印单词序列

我在寻找什么：

a = [0,13,26,39]
b = [12,25,38,51]

str = 'If you are done with the file, move to the command area across from the file name in the RL screen and type'

read = str.split()

read[0:12]
['If', 'you', 'are', 'done', 'with', 'the', 'file,', 'move', 'to', 'the', 'command', 'area']
read[13:25]
['from', 'the', 'file', 'name', 'in', 'the', 'RL', 'screen', 'and', 'type']

【问题讨论】：

嗯，有什么问题？
请问，您是在什么情况下发现这样的问题的？

标签： python string python-2.7

【解决方案1】：

使用zip:

>>> a = [0,13,26,39]
>>> b = [12,25,38,51]
>>> strs = 'If you are done with the file, move to the command area across from the file name in the RL screen and type'
>>> spl = strs.split()
>>> for x,y in zip(a,b):
...     print spl[x:y]
...     
['If', 'you', 'are', 'done', 'with', 'the', 'file,', 'move', 'to', 'the', 'command', 'area']
['from', 'the', 'file', 'name', 'in', 'the', 'RL', 'screen', 'and', 'type']
[]
[]

zip 返回元组列表，其中每个元组包含来自传递给它的可迭代对象的同一索引上的项：

>>> zip(a,b)
[(0, 12), (13, 25), (26, 38), (39, 51)]

如果您想要内存高效的解决方案，请使用itertools.izip，因为它返回一个迭代器。

如果您想从该切片列表创建一个字符串，您可以使用str.join：

for x,y in zip(a,b):
    print " ".join(spl[x:y])
...     
If you are done with the file, move to the command area
from the file name in the RL screen and type

更新：创建a 和b：

>>> n = 5
>>> a = range(0, 13*n, 13)
>>> b = [ x + 12 for x in a]
>>> a
[0, 13, 26, 39, 52]
>>> b
[12, 25, 38, 51, 64]

【讨论】：

我怎样才能创建列表a和b。这些是在 a 和 b 的情况下 N+1 个数多 13 的序列。还有 b[0] = a[0] + 12

【解决方案2】：

你的意思是：

>>> [read[i:j] for i, j in zip(a,b)]
[['If', 'you', 'are', 'done', 'with', 'the', 'file,', 'move', 'to', 'the', 
'command',    'area'], ['from', 'the', 'file', 'name', 'in', 'the', 'RL',
'screen', 'and', 'type'], [], []]

或

>>> ' '.join[read[i:j] for i, j in zip(a,b)][0])
'If you are done with the file, move to the command area'

>>> ' '.join[read[i:j] for i, j in zip(a,b)][1])
'from the file name in the RL screen and type'

【讨论】：

【解决方案3】：

a = [0,13,26,39]
b = [12,25,38,51]
str = 'If you are done with the file, move to the command area across from the file name  in the RL screen and type'

read = str.split()
extra_lists = [read[start:end] for start,end in zip(a,b)]
print extra_lists

【讨论】：

【解决方案4】：

你提到了一个 lambda，所以：

 f = lambda s, i, j: s.split()[i:j]
 >>> f("hello world how are you",0,2)
 ['hello', 'world']

好像你在两个列表中做切片索引，我可以建议一个字典或一个元组列表吗？

str = 'If you are done with the file, move to the command area across from the file name in the RL screen and type'
slices = [(0, 13), (12, 25)]
dslices = {0:13, 12:25}
for pair in slices:
    print f(str, pair[0], pair[1])
for key in dslices:
    print f(str, key, dislikes[key])

当您可以选择更好地格式化数据时，我不喜欢使用 zip。

【讨论】：