Can anybody explain how this piece of code knows the integer value of "shift-val" so it subtracts it from the ASCII value of character
alpha=['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z']
def encodeMessage(message,shift_val):
encodedMessage = ""
l = len(alpha)
length = len(message)
for i in range(0,length):
# ord returns ASCII value of character, we add shift_val to it and
subtract ASCII value of 'A'
x = ord(message[i])+shift_val- ord('A')
# x could exceed 26, we need to cycle back hence mod 26 is used.
x = x % 26
# add xth index alphabet to encoded message
encodedMessage += alpha[x]
# return encodedMessage
return encodedMessage
def main():
# message will be a string
message = ""
UserInput = input("Enter maximum 10 upper-case letters in one line to store: ")
lengthAlpha= len(alpha)
while not UserInput.isalpha() or len(UserInput) > 10 : # message is not acceptable in case it's greater than ten or it isn't a letter
print (" No special characters numbers are allowed (maximum 10 letters) ")
UserInput = input("Enter maximum 10 upper-case letters in one line to store: ")
else:
message =UserInput
message = [element.upper() for element in message]
move = int(input("How far do you wish to shift?: "))
print('The encoded message is',encodeMessage(message, move))
main()
The user is asked for an amount to "shift". This value is stored in a variable called move as an integer:
move = int(input("How far do you wish to shift?: "))
This value is passed into encode_message(), where it is bound to the shift_val parameter:
print('The encoded message is',encodeMessage(message, move))
encodeMessage() knows the value of shift_val because it gets passed into the function as an argument. In another context shift_val could have any other value; it depends entirely on how the function is called.