How To Iterate Over Each String In A List Of Strings And Operate On It's Elements

Im new to python and i need some help with this. TASK : given a list --> words = ['aba', 'xyz', 'xgx', 'dssd', 'sdjh'] i need to compare the first and the last element of each

Solution 1:

Try:

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

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

for idx, word inenumerate(words):
    print idx, word

would output

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

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.

You can also use a generator to achieve this.

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

Solution 2:

The reason is that in your second example i is the word itself, not the index of the word. So

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

would the equivalent of your code.

Solution 3:

The suggestion that using range(len()) is the equivalent of using enumerate() is incorrect. They return the same results, but they are not the same.

Using enumerate() actually gives you key/value pairs. Using range(len()) does not.

Let's check range(len()) first (working from the example from the original poster):

words = ['aba', 'xyz', 'xgx', 'dssd', 'sdjh']
    printrange(len(words))

This gives us a simple list:

[0, 1, 2, 3, 4]

... and the elements in this list serve as the "indexes" in our results.

So let's do the same thing with our enumerate() version:

words = ['aba', 'xyz', 'xgx', 'dssd', 'sdjh']    
   printenumerate(words)

This certainly doesn't give us a list:

<enumerateobject at 0x7f6be7f32c30>

...so let's turn it into a list, and see what happens:

printlist(enumerate(words))

It gives us:

[(0, 'aba'), (1, 'xyz'), (2, 'xgx'), (3, 'dssd'), (4, 'sdjh')]

These are actual key/value pairs.

So this ...

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

for i inrange(len(words)):
    print"words[{}] = ".format(i), words[i]

... actually takes the first list (Words), and creates a second, simple list of the range indicated by the length of the first list.

So we have two simple lists, and we are merely printing one element from each list in order to get our so-called "key/value" pairs.

But they aren't really key/value pairs; they are merely two single elements printed at the same time, from different lists.

Whereas the enumerate () code:

for i, word inenumerate(words):
    print"words[{}] = {}".format(i, word)

... also creates a second list. But that list actually is a list of key/value pairs, and we are asking for each key and value from a single source -- rather than from two lists (like we did above).

So we print the same results, but the sources are completely different -- and handled completely differently.

Solution 4:

The following code outputs the number of words whose first and last letters are equal. Tested and verified using a python online compiler:

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

Output:

$python main.py
3

Solution 5:

c=0
words = ['challa','reddy','challa']

for idx, word inenumerate(words):
    if idx==0:
        firstword=word
        print(firstword)
    elif idx == len(words)-1:
        lastword=word
        print(lastword)
        if firstword==lastword:
            c=c+1print(c)