Python: How do I reverse every other string in a list?

Here's one simple way to do it:

>>> s = ['Bananas', 'Apples', 'Fruits', 'Chocolate', 'Watermelon', 'Kiwi', 'Avacado', 'Lemon', 'Lime', 'Money']
>>> for i in range(1, len(s), 2):
        s[i] = s[i][::-1]

>>> s
['Bananas', 'selppA', 'Fruits', 'etalocohC', 'Watermelon', 'iwiK', 'Avacado', 'nomeL', 'Lime', 'yenoM']

The range(1, len(s), 2) starts at position 1 and counts by twos.

The [::-1] reverses a string.

I feel many of the solutions posted are quite clever, but may feel slightly too comprehendible for a beginner. This solution is not simple and uses a single step to achieve the result.

>>> x = ['Bananas', 'Apples', 'Fruits', 'Chocolate', 'Watermelon', 'Kiwi', 'Avacado', 'Lemon', 'Lime', 'Money']
>>> [v[::1-(i%2)*2] for i, v in enumerate(x)]
['Bananas', 'selppA', 'Fruits', 'etalocohC', 'Watermelon', 'iwiK', 'Avacado', 'nomeL', 'Lime', 'yenoM']

You can reverse a string word by writing word[::-1], so the task is just to apply this for every other element. This can be solved with a list comprehension, using enumerate and checking whether the index is odd or even.

>>> words = ['Bananas', 'Apples', 'Fruits', 'Chocolate', 'Watermelon',
             'Kiwi', 'Avacado', 'Lemon', 'Lime', 'Money']
>>> [ (word if i%2 == 0 else word[::-1]) for i, word in enumerate(words) ]
['Bananas', 'selppA', 'Fruits', 'etalocohC', 'Watermelon', 'iwiK',
 'Avacado', 'nomeL', 'Lime', 'yenoM']

I feel many of the solutions posted are quite clever, but may feel slightly impenetrable to a beginner. This solution is quite simple and uses simple steps to achieve the result.

words = ['Bananas', 'Apples', 'Fruits', 'Chocolate', 'Watermelon', 'Kiwi', 'Avacado', 'Lemon', 'Lime', 'Money']

for index in range(0,len(words)):
    if index%2 != 0: #find every other 'index'
        words[index] = words[index][::-1] #reverse word at every other 'index'

In one line:

list1 = ['Bananas', 'Apples', 'Fruits', 'Chocolate', 'Watermelon', 'Kiwi', 'Avacado', 'Lemon', 'Lime', 'Money']

[x[::-1] if i % 2 != 0 else x for i, x in enumerate(list1)]
['Bananas',
 'selppA',
 'Fruits',
 'etalocohC',
 'Watermelon',
 'iwiK',
 'Avacado',
 'nomeL',
 'Lime',
 'yenoM']

You could use map for iterating and enumerate to get the index. Check if the index is odd and then reverse using [::-1]

Python 2

>>> v=['Bananas', 'Apples', 'Fruits', 'Chocolate', 'Watermelon', 'Kiwi', 'Avacado', 'Lemon', 'Lime', 'Money']
>>> map( lambda (i,x): x[::-1] if i % 2 == 1 else x , enumerate(v))
['Bananas', 'selppA', 'Fruits', 'etalocohC', 'Watermelon', 'iwiK', 'Avacado', 'nomeL', 'Lime', 'yenoM']

Python 3

list(map( lambda x: x[1][::-1] if x[0] % 2 == 1 else x[1] , enumerate(v)))

The above will give a new list. If you want same list to be modified, then

 >>> v=['Bananas', 'Apples', 'Fruits', 'Chocolate', 'Watermelon', 'Kiwi', 'Avacado', 'Lemon', 'Lime', 'Money']
 >>> for i,x in enumerate(v):
  ...  if i %2 == 1:
  ...    v[i]=v[i][::-1]
 >>> v
['Bananas', 'selppA', 'Fruits', 'etalocohC', 'Watermelon', 'iwiK', 'Avacado', 'nomeL', 'Lime', 'yenoM']

You can iterate through your list by 2 like so

for word in my_words[::2]:
    print(reversed(word)) 

This will step through your array but 2 and will print the word in reversed. You can also reverse a word by using word[::-1]