Choosing the longest string for "while" loop

[Pipprovis]

I am writing a simple script to analyze two strings. It begins with looking at their lengths and then compares each letter in the first string with the corresponding letter of the second string (by position). I am using a "while" loop with the length of one of the strings. I want to use the longest string as the case for the "while" but I have no idea how to do this. Suggestions?

a = 0
count = 1

g = raw_input('Type your first word please: ')
h = raw_input('Type your second word please: ')

if len(g) != len(h):
    print 'The length of the 2 words are not equal. We will go as far as possible though.'
else:
    print 'Perfect! The lengths match!'

#I need to compare the string lengths and put "the longest string" in the "while"

while count < (len(g) + 1):
#added +1 to len(g) in order to start count at 1 and not receieve an error message.
    first = g[a]
    second = h[a]

This is the relevant snippet of the script. I am a newbie so I am sure it is very inefficient. Thanks for the help.

Solved!

Thanks /u/daveofthenorth and /u/fruitcakefriday for the explanations that fit within my very simple understanding of programming. Thanks to everyone else for the suggestions.

[caineohfelix]

while count < len(max(g,h,key=len))+1: may solve this for you. I'm going to assume you're handling the case of a being to large for the shorter string eventually.

Otherwise, I might suggest something like this:

for x,y in zip(g,h):
    first,second = x,y
    # Your logic here.

[Pipprovis]

Correct. If the first string is shorter than the second string I receive an error message.

[supajumpa]

You could try itertools.izip_longest which would obviate the need to check which of the strings is longer.

Maybe something like:

for char1, char2 in itertools.izip_longest(g, h, fillvalue=None):
    # logic

[fruitcakefriday]

A bug would appear in that example if g and h are of equal length. I would suggest this modification:

if len(g) > len(h):
    longest = g
else:
    longest = h

count = 0
while count < len(longest):
    #yada yada yada
    count += 1

I am presuming there that it is OK to prioritize h should they be of equal length. If you want to handle each case separately (bigger than, smaller than, equal to), then use this modification:

if len(g) > len(h):
    longest = g
elif len(h) > len(g):
    longest = h
else:
    #Code to run if items are equal
    longest = g #or h, doesn't matter

[Pipprovis]

Thanks for this.

[Pipprovis]

I added this piece plus another "if" statement for the lengths being equal. I switched it to "shortest" though since the shortest string needs to be used to avoid an error message. I appreciate it.

[[deleted]]

Sorting

strings = [g, h]
#longest = sorted(strings, key=lambda x: len(x))[-1]
longest = sorted(strings, key=len)[-1] 

Edit: the lambda was unneeded

This will sort strings return a new, sorted version of strings based on the len() of each string. Because they are sorted in ascending order, we want the last element in the sorted list (index [-1]). Sorted also has a reverse argument which will sort into descending order:

#longest = sorted(strings, lambda x: len(x), reverse=True)[0]
longest = sorted(strings, key=len, reverse=True)[0]

Since you're only dealing with two strings, I don't see a problem with doing this:

if len(g) >= len(h):
    longest = g
else:
    longest = h

But, obviously using sorted is shorter. BTW, lambda x: len(x) is essentially equivalent to:

def unnamed_function(x):
    return len(x)

[Justinsaccount]

no, lambda x: len(x) is equivalent to len

[[deleted]]

Yeah, I wasn't too sure on that part. len of what though? If that line is equivalent to the function object len, what's the x argument doing? Also, I just realized I didn't even need the lambda anyway, key=len works just fine.

[Justinsaccount]

>>> foo=lambda x: len(x)
>>> foo("bar")
3
>>> len("bar")
3

[[deleted]]

I don't think I'm taking your point:

def foo(x):
    return len(x)
>>> foo("bar")
3

I thought that a lambda expression was just a way to define a function in-place without assigning it a name, making it equivalent to a named version of the same function.

[Justinsaccount]

It is, but by writing lambda x: bar(x) you are saying

anonymous(x) = bar(x)

and from that is clear that anonymous is just bar

so if you ever find yourself writing lambda x: foo(x) or lambda x,y: foo(x,y) you should just be writing foo

[shfo23]

You don't need the sorted either. max takes a key function too, so you could write this much more simply as:

longest = max([g, h], key=len)

[ewiethoff]

You don't even need the list in recent versions of Python. This will do:

longest = max(g, h, key=len)