查找字符串列表中的元素

Question

I have a string, 'RTKLOANGMSTTTS' and a list of tuples, [(2,5),(8,9)], that returns a string containing the letters 2-5 and 8-9 both inclusive, that is 'TKLOGM'. I was thinking something like:

def f(string, lst):
    for element in lst:
        if element in string:
            print string

But it does not return anything?

Answer 1

Try this:

def f(source, lst):
    return "".join(source[start - 1:end] for start, end in lst)

What this will do is iterate over the lst , extracting the tuple into start and end on every iteration. Then it will create a new string as a slice from the source string, from start - 1 to end (we use start - 1 because you showed that 1 means the first character, but python uses 0-indexing, so we must substract one). Finally we join all the strings using "".join() .

If you use an older version of Python that doesn't support the generator syntax, use this instead:

def f(source, lst):
    return "".join([source[start - 1:end] for start, end in lst])

It works exactly the same, but instead of working with a generator it explicitly creates a list which gets joined.

Answer 2

>>> x = 'RTKLOANGMSTTTS'
>>> l = [(2,5),(8,9)]
>>> ''.join(x[s-1:e] for (s,e) in l)
'TKLOGM'

Answer 3

I think this is what you asking for. I can't test right now, but try:

def f(string, lst):
    getStr = ''
    for t in lst:
        begin, end = t
        getStr += string[begin-1:end]
    return getStr

Answer 4

def f(string, lst):
   for start, end in lst:
       s = string[start-1:end]
       if s:
           yield s

for s in f('RTKLOANGMSTTTS', [(2,5),(8,9)]):
    print s