Python Caesar Cipher Using Turkish Alphabet Array

I would reorganize your code, to make it look more like this:

def ceasercypher(steps, word):
        alpLower,  alpUpper = ["a", "b", "c", "ç", "d", "e", "f", "g", "ğ", "h", "ı", "i", "j", "k", "l", "m", "n", "o", "ö", "p", "r",
                    "s", "ş", "t", "u", "ü", "v", "y", "z"], ["A", "B", "C", "Ç", "D", "E", "F", "G", "Ğ", "H", "I", "İ", "J", "K", "L", "M", "N", "O", "Ö", "P", "R",
                    "S", "Ş", "T", "U", "Ü", "V", "Y", "Z"]
        answer = []
        for letter in word:
            if letter.isupper():
                answer.append(alpUpper[int((steps + alpUpper.index(letter))%len(alpUpper))])
            if letter.islower():
                answer.append(alpLower[int((steps + alpLower.index(letter))%len(alpLower))])
        return "".join(answer)
print(ceasercypher(0, "ağV"))

just for fun, you can always try to write it short! but if you work in a team or, want to be able to understand it later this is bad practice. I call it "programmers useless flex, and root of a lot of bugs"

def ceasercypher(steps, word):
    alpLower,  alpUpper = ["a", "b", "c", "ç", "d", "e", "f", "g", "ğ", "h", "ı", "i", "j", "k", "l", "m", "n", "o", "ö", "p", "r",
                "s", "ş", "t", "u", "ü", "v", "y", "z"], ["A", "B", "C", "Ç", "D", "E", "F", "G", "Ğ", "H", "I", "İ", "J", "K", "L", "M", "N", "O", "Ö", "P", "R",
                "S", "Ş", "T", "U", "Ü", "V", "Y", "Z"]
    return "".join([alpUpper[int((steps + alpUpper.index(letter))%len(alpUpper))] if letter.isupper() else alpLower[int((steps + alpLower.index(letter))%len(alpLower))] if letter.islower() else " [INVALIDCHAR] " for letter in word])
print(ceasercypher(1, "ağVZ%K%"))

Actually, you don't need to loop through each element in the list to know what it's index is, you can just get the index with the element using index().

animals = ['cat', 'dog', 'giraffe', 'elephant', 'monkey']
  
# Will print the index of 'giraffe' in animals
print(animals.index('giraffe'))

Output:

Applying it to your code:

for c in text:
    if c in alpUpper:
        i = alpUpper.index(c)
        c = alpUpper[(i + shift) % 29]
        b += 1
        encrypt.append(c)
    else:
        b == 0