[英]How to slice a string in Python using a dictionary containing character positions?
[英]How to use Python slice to extract a list of positions in a string
我有兩個字符串:
a='1234512345'
b='abcdefghik'
我想搜索字符串“a”出現'1',然后打印對應於該索引的“b”的位置,即
'af'
我可以用
import re
starts=[match.start() for match in re.finditer(re.escape('1'), a)]
發現位置[0,5]中出現'1'。 如何使用此信息從字符串“b”中提取“af”
你可以這樣做:
''.join(b[x] for x in starts)
但我建議這樣做:
a='1234512345'
b='abcdefghik'
''.join(y for (x, y) in zip(a, b) if x == '1')
>>> a='1234512345'
>>> b='abcdefghik'
>>> [ j for i,j in zip(a,b) if i=="1" ]
['a', 'f']
In [11]: a='1234512345'
In [12]: b='abcdefghik'
In [16]: ''.join(b[i] for i,num in enumerate(a) if num=='1')
Out[16]: 'af'
或者,如果你真的想使用正則表達式:
In [21]: ''.join(b[match.start()] for match in re.finditer(re.escape('1'), a))
Out[21]: 'af'
import re
a='1234512345'
b='abcdefghik'
starts= [ b[i] for i in [ match.start() for match in re.finditer(re.escape('1'), a)]]
print ''.join(starts)
"".join(b[i] for i in range(min(len(a), len(b))) if a[i] == "1")
像這樣?
a='1234512345'
b='abcdefghik'
for char in a:
n = -1
for subc in a:
n=n+1
if subc == char:
print b[n],
print
生產:
a f
b g
c h
d i
e k
a f
b g
c h
d i
e k
如果你需要重復此為幾個值a
,這將是更有效的((O(N))來構建字典,而不是通過環a
和b
反復(O(N * N))
>>> a='1234512345'
>>> b='abcdefghik'
>>> from collections import defaultdict
>>> D=defaultdict(str)
>>> for i,j in zip(a,b):
... D[i]+=j
...
>>> D['1']
'af'
>>> D['2']
'bg'
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