Python's most efficient way to choose longest string in list?

From the Python documentation itself, you can use max:

>>> mylist = ['123','123456','1234']
>>> print max(mylist, key=len)
123456

def longestWord(some_list): 
    count = 0    #You set the count to 0
    for i in some_list: # Go through the whole list
        if len(i) > count: #Checking for the longest word(string)
            count = len(i)
            word = i
    return ("the longest string is " + word)

or much easier:

max(some_list , key = len)

What should happen if there are more than 1 longest string (think '12', and '01')?

Try that to get the longest element

max_length,longest_element = max([(len(x),x) for x in ('a','b','aa')])

And then regular foreach

for st in mylist:
    if len(st)==max_length:...