iterating strings in python with for loop

Your code.

n = ["Michael", "Lieberman"]

def join_strings(words):
    # words = ["Michael", "Lieberman"]
    result = ""
    for i in words:
        # i = 'Michael' for the first iteration.
        # if you do range(len(words)) then i=0 and words[0] is valid then
        result += words[i] #<--Error! i='Michael' and you can't do words['Michael']
    return result

print join_strings(n)

Pythonic way of joining strings in the list:

print ''.join(n) #Outputs --> MichaelLieberman

i is a string value not index. You can use enumerate function:

for index, i in enumerate(words): 
    result += words[index]

or you can just use the word itself:

for i in words:
    result += i

Performance:

In [14]: timeit.timeit('string_cat', '''def string_cat():
    ...:     rg = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
    ...: 't', 'u', 'v', 'w', 'x', 'y', 'z']
    ...:     st = ''
    ...:     for x in rg: st += x
    ...: ''', number=1000000)
Out[14]: 0.02700495719909668

In [15]: timeit.timeit('string_cat', '''def string_cat():
    ...:     rg = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
    ...: 't', 'u', 'v', 'w', 'x', 'y', 'z']
    ...:     st = ''.join(rg)
    ...: ''', number=1000000)
Out[15]: 0.026237964630126953

if you r using for loop like :

for i in words:

then do like this :

result += i

because here we are taking values from list directly without mentioning any range or it's size.

if u r using for loop like :

for i in range(len(words)):

then do like this :

result += words[i]

and the output will be same from both the cases :

MichaelLieberman

for better clarification about for loop refer this : https://www.learnpython.org/en/Loops