Adding strings in lists together

Question

I want to transform the list ["A","B","A","A","B"] to the list ["AB","BA","AA","AB"].

I have tried to define a new list in which the first element is deleted and then add the strings of the lists together. After which I plan to delete the last element of the new list to get the result.

lista = sequences
lista.pop(0)
print(lista)

for x in range(sequences):
    mc =sequences[x]+lista[x]

But all I get is

TypeError: 'list' object cannot be interpreted as an integer

Any help is welcome.

Edit : Thank you guys, all your solutions worked perfectly :)

Answer 1

Best solution, using zip, cleverest:

>>> l = ["A","B","A","A","B"]
>>> [x + y for x, y in zip(l, l[1:])]
['AB', 'BA', 'AA', 'AB']
>>> 

Or use this list comprehension:

>>> l = ["A","B","A","A","B"]
>>> [v + l[i + 1] for i, v in enumerate(l[:-1])]
['AB', 'BA', 'AA', 'AB']
>>> 

Answer 2

Use zip():

>>> lst = ["A","B","A","A","B"]
>>> [x + y for x, y in zip(lst, lst[1:])]
['AB', 'BA', 'AA', 'AB']

Answer 3

您可以使用map()：

s = list(map(str.__add__, lst[:-1], lst[1:]))

更好用operator.concat()（感谢建议，@ MykolaZotko）：

import operator

s = list(map(operator.concat, lst[:-1], lst[1:]))

更新。

我决定对更大的数据进行一些测试。

import operator

lst = [...] # list with 10000 random uppercase letters


def test1():
    return list(map(operator.concat, lst[:-1], lst[1:]))


def test2():
    return [x + y for x, y in zip(lst, lst[1:])]


def test3():
    return [v + lst[i + 1] for i, v in enumerate(lst[:-1])]


def test4():
    s = ''.join(lst)
    return [s[i:i + 2] for i in range(len(s) - 1)]


if __name__ == '__main__':
    import timeit
    print(timeit.timeit("test1()", setup="from __main__ import test1, lst", number=10000))
    print(timeit.timeit("test2()", setup="from __main__ import test2, lst", number=10000))
    print(timeit.timeit("test3()", setup="from __main__ import test3, lst", number=10000))
    print(timeit.timeit("test4()", setup="from __main__ import test4, lst", number=10000))

结果：

1. Python 2：

   10.447159509
   11.529946446
   20.962497298000002
   20.515838672
   

2. Python 3：

   10.370675522
   11.429417197
   20.836504865999995
   20.422865353
   

在更大的数据map()是有点（〜9％）快，但有之间没有显著差异test1()和test2()