Polish to cyrillic text converter

polishToCyrillic.py

#!/bin/python3
mainMap = {
    "a": "а",
    "ą": "ѧ",
    "b": "б",
    "c": "ц",
    "ć": "ть",
    "d": "д",
    "e": "э",
    "ę": "ѫ",
    "f": "ф",
    "g": "ґ",
    "h": "г",
    "i": "и",
    "j": "й",
    "k": "к",
    "l": "л",
    "ł": "ў",
    "m": "м",
    "n": "н",
    "ń": "нь",
    "o": "о",
    "ó": "у",
    "p": "п",
    "r": "р",
    "s": "с",
    "ś": "сь",
    "t": "т",
    "u": "у",
    "w": "в",
    "y": "ы",
    "ź": "зь",
    "ż": "ж"
}

iotatedVowels = {"a": "я", "e": "е", "o": "ё", "u": "ю", "ą": "ѩ", "ę": "ѭ"}

def toCyrillic(text):
    text = text.lower().replace("ti", "tъi").replace("ci", "ti")
    outputText = []

    for index, letter in enumerate(text):
        previousLetter = text[index - 1] if index > 0 else " "

        if letter in iotatedVowels.keys() and (previousLetter == "j" or previousLetter == "i"):
            if index > 1 and previousLetter == "j" and text[index - 2] in ["n", "s", "z", "t"]:
                outputText[-1] = "ъ"
                outputText += iotatedVowels[letter]
            else:
                outputText[-1] = iotatedVowels[letter]
        elif letter == "z":
            if previousLetter == "c":
                if index > 2 and text[index - 2] == "z" and text[index - 3] == "s":
                    outputText[-1] = "щ"
                else:
                    outputText[-1] = "ч"
            elif previousLetter == "s":
                outputText[-1] = "ш"
            elif previousLetter == "r":
                outputText[-1] = "ж"
            else:
                outputText += "з"
        elif letter == "h" and previousLetter == "c":
            outputText[-1] = "х"
        elif letter in mainMap.keys():
            outputText += mainMap[letter]
        else:
            outputText += letter

    return "".join(outputText)

if __name__ == "__main__":
    open("output.txt", "w").write(toCyrillic(open("input.txt", "r").read()))