如何遍历字符串列表中的每个字符串并对其元素进行操作 [英] How to iterate over each string in a list of strings and operate on it's elements

问题描述

我是python的新手，我需要一些帮助.

Im new to python and i need some help with this.

任务:给出一个列表-> words = ['aba', 'xyz', 'xgx', 'dssd', 'sdjh']

TASK : given a list --> words = ['aba', 'xyz', 'xgx', 'dssd', 'sdjh']

我需要比较列表中每个字符串的第一个和最后一个元素， 如果字符串中的第一个元素和最后一个元素相同，则增加计数.

i need to compare the first and the last element of each string in the list, if the first and the last element in the string is the same , then increment the count.

列表为:

words = ['aba', 'xyz', 'xgx', 'dssd', 'sdjh']

如果我手动尝试，我可以遍历列表中字符串的每个元素.

If i try manually, i can iterate over each element of the strings in the list.

words = ['aba', 'xyz', 'xgx', 'dssd', 'sdjh']
w1 = words[0]
print w1
aba

for i in w1:
   print i

a
b
a

if w1[0] == w1[len(w1) - 1]:
   c += 1
   print c

1

但是，当我尝试使用FOR循环遍历列表中所有字符串的所有元素时.

But, When i try to iterate over all the elements of all the strings in the list , using a FOR loop.

我得到一个错误.

words = ['aba', 'xyz', 'xgx', 'dssd', 'sdjh']
c = 0
for i in words:
     w1 = words[i]
     if w1[0] == w1[len(w1) - 1]:
       c += 1
     print c

错误:

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
TypeError: list indices must be integers, not str

请让我知道，如何比较否的第一个元素和最后一个元素.列表中的字符串.

please let me know, how would i achieve comparing the first and the last element of a no. strings in the list.

谢谢.

推荐答案

尝试:

for word in words:
    if word[0] == word[-1]:
        c += 1
    print c

for word in words返回words的项目，而不是索引.如果您有时需要索引，请尝试使用enumerate:

for word in words returns the items of words, not the index. If you need the index sometime, try using enumerate:

for idx, word in enumerate(words):
    print idx, word

将输出

0, 'aba'
1, 'xyz'
etc.

上面word[-1]中的-1是Python所说的最后一个元素"的方式. word[-2]将给您倒数第二个元素，依此类推.

The -1 in word[-1] above is Python's way of saying "the last element". word[-2] would give you the second last element, and so on.

您还可以使用生成器来实现这一目标.

You can also use a generator to achieve this.

c = sum(1 for word in words if word[0] == word[-1])

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