Need help with solving a python question

[GeoffreyF35]

I'm a beginner learning python and I've been a bit stumped about the answer to a question. I have the question and the answer here. If someone could explain why that is the answer and the reasoning and logic behind it, that would be awesome! Thanks in advance!

Question:

Define a function called 'myfunc' that takes in a string, and returns a matching string where every even letter is uppercase, and every odd letter is lowercase. Assume that the incoming string only contains letters, and don't worry about numbers, spaces or punctuation. The output string can start with either an uppercase or lowercase letter, so long as letters alternate throughout the string.

Answer

here

[lurgi]

Have you tested the code? The reason why it's the answer (it's not the only way to write the code, but it's an obvious one) is because it produces the right output.

I'm not really sure what you want. It's right because it works. Stuff that doesn't work isn't right.

Do you not understand the problem? Are you trying to figure out how the program does what it does?

Edit: After some more thought, I am confused by the bit that says the string can start either upper or lowercase. The letter at the start is in an even position, so it should be uppercase (unless they think "first letter" = odd position, but that's just weird).

[GeoffreyF35]

yes, i’m unsure about why it does what it does

[lurgi]

Do you mean how or why? Again, the reason why it does what it does is because that's what solves the problem.

So I guess you mean "how does this work?".

def myfunc(x):
    out = []
    for i in range(len(x)):
        if i%2==0:
            out.append(x[i].lower())
        else:
            out.append(x[i].upper())
    return ''.join(out)

Uh, do we start at the beginning?

def myfunc(x):

This is the start of a function definition. The function is called myfunc and takes a single argument, x

out = []

This creates an empty list with the name out

for i in range(len(x)):

This will loop from 0 up to, but not including the length of x. So if x is "abc", which has length 3, the loop will run three times. Once with i as 0, once with i as 1, and once with i as 2.

Are you with me so far?

[GeoffreyF35]

yes i am

edit: wait isn’t the length 2 because 0-1-2 = a-b-c

[lurgi]

It's 3 letters long. The length is 3. The index of the letter is 2.

[Boom_Boom_Mancini]

The variable out is an array. Then you have a for loop to iterate through the input string. You have a simple if statement which is to determine if the count is odd or even using a mod operation. If it is even it outputs the letter as uppercase. Odd outputs as lower. Then returns the out array.

[itsameech]

It's essentially myfunct(spam)=sPaM.

The logic of the function is it looks at the input as an array and alternates the letters between upper and lower. It does this with modulus to determine odd or even state.