[英]What's the pythonic way to split a string using a list of sizes?
What's the pythonic way to implement this: 实现这个的pythonic方法是什么:
s = "thisismystring"
keys = [4, 2, 2, 6]
new = []
i = 0
for k in keys:
new.append(s[i:i+k])
i = i+k
This does give me ['this', 'is', 'my', 'string']
as I need but I fell there's a more elegant way to do it. 这确实给了我['this', 'is', 'my', 'string']
,但是我觉得这是一种更优雅的方式。 Suggestions? 建议?
You could use itertools.accumulate()
, perhaps: 您可以使用itertools.accumulate()
,也许:
from itertools import accumulate
s = "thisismystring"
keys = [4, 2, 2, 6]
new = []
start = 0
for end in accumulate(keys):
new.append(s[start:end])
start = end
You could inline the start
values by adding another accumulate()
call starting at zero: 你可以内联start
通过增加另一个值accumulate()
从零开始电话:
for start, end in zip(accumulate([0] + keys), accumulate(keys)):
new.append(s[start:end])
This version can be made into a list comprehension: 这个版本可以制成列表理解:
[s[a:b] for a, b in zip(accumulate([0] + keys), accumulate(keys))]
Demo of the latter version: 演示后者版本:
>>> from itertools import accumulate
>>> s = "thisismystring"
>>> keys = [4, 2, 2, 6]
>>> [s[a:b] for a, b in zip(accumulate([0] + keys), accumulate(keys))]
['this', 'is', 'my', 'string']
The double accumulate could be replaced with a tee()
, wrapped in the pairwise()
function from the itertools
documentation : double accumulate可以替换为tee()
,包含在itertools
文档中的itertools
pairwise()
函数中 :
from itertools import accumulate, chain, tee
def pairwise(iterable):
"s -> (s0,s1), (s1,s2), (s2, s3), ..."
a, b = tee(iterable)
next(b, None)
return zip(a, b)
[s[a:b] for a, b in pairwise(accumulate(chain([0], keys)))]
I threw in an itertools.chain()
call to prefix that 0 starting position, rather than create a new list object with concatenation. 我在一个itertools.chain()
调用中输入前缀为0的起始位置,而不是创建一个带有连接的新列表对象。
I would use enumerate
for that, with accumulating: 我会使用enumerate
,累积:
[s[sum(keys[:i]): sum(keys[:i]) + k] for i, k in enumerate(keys)]
With your example: 用你的例子:
>>> s = "thisismystring"
>>> keys = [4, 2, 2, 6]
>>> new = [s[sum(keys[:i]): sum(keys[:i]) + k] for i, k in enumerate(keys)]
>>> new
['this', 'is', 'my', 'string']
Could use islice
. 可以使用islice
。 Probably not efficient, but maybe at least interesting and simple. 可能效率不高,但可能至少有趣而且简单。
>>> from itertools import islice
>>> s = 'thisismystring'
>>> keys = [4, 2, 2, 6]
>>> it = iter(s)
>>> [''.join(islice(it, k)) for k in keys]
['this', 'is', 'my', 'string']
Just because I believe there have to be ways to do this without explicit loops: 仅仅因为我认为必须有办法在没有显式循环的情况下做到这一点:
import re
s = "thisismystring"
keys = [4, 2, 2, 6]
new = re.findall((r"(.{{{}}})" * len(keys)).format(*keys), s)[0]
print(new)
OUTPUT OUTPUT
('this', 'is', 'my', 'string')
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