[Python] Bruteforcing the ceaser cipher

I wanted to write an algorithm for bruteforcing shift ciphers based on the Ceaser cipher decryption algorithm that I implemented in Python as below

letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
def decrypt(cipher: str):
"Decrypts text encrtyted in Ceaser's cipher"
plaintext = []
for i in cipher:
p = (letters.find(i) - 3) % 26 #Decryption algorithm: p = (c-k) mod 26
#where; c is the index of the letter in the alphabet and k is the key
if i == "-":
plaintext.append(" ")
else:
if p < 0: #if the number is a negative, ignore mod 26 and instead, directly sum to 26
p = p + 26
else:
plaintext.append(letters[p])
return "".join(plaintext)


I tried wrapping the code around a while loop to cycle through the possible combinations but everything just broke.

def bruteforce(cipher: str):
"Cycles through all possible shifts"
n = 1
while n <= 26:
plaintext = []
for i in cipher.upper():
p = (letters.find(i) - n) % 26
if i == "-":
plaintext.append(" ")
else:
if p < 0:
p = p + 26
else:
plaintext.append(letters[p])

n += 1
return "".join(plaintext)


Any ideas on what I did wrong?

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