Question

I have two functions.
The first will build a coder to Caesar cipher a given text:

def buildCoder(shift):

        lettersU=string.ascii_uppercase
        lettersL=string.ascii_lowercase
        dic={}
        dic2={}

        for i in range(0,len(lettersU and lettersL)):
            dic[lettersU[i]]=lettersU[(i+shift)%len(lettersU)]
            dic2[lettersL[i]]=lettersL[(i+shift)%len(lettersL)]
        dic.update(dic2)
        return dic

The second will apply the coder to a given text:

def applyCoder(text, coder):
        cipherText=''
        for l in text:
            if l in coder:
                l=coder[l]
            cipherText+=l
        return cipherText

Part 3 of the problem asks me to build a wrapper, but as I am new to coding I have no idea how to code a wrapper that uses these two functions.

def applyShift(text, shift):
  """
  Given a text, returns a new text Caesar shifted by the given shift
  offset. Lower case letters should remain lower case, upper case
  letters should remain upper case, and all other punctuation should
  stay as it is.

  text: string to apply the shift to
  shift: amount to shift the text (0 <= int < 26)
  returns: text after being shifted by specified amount.
  """

Answer 1

Think of each of your functions as something that takes a certain kind of data and gives you a different kind.

buildCoder takes a shift and gives you a coder.

applyCoder takes some text (a string to be coded) and a coder and gives you the coded string.

Now, you want to write applyShift, a function that takes a shift and some text and gives you the coded string.

Where can you get the coded string? Only from applyCoder. It needs text and a coder. We have the text because it was given to us, but we also need a coder. So let’s get the coder from buildCoder using the shift that we were provided.

Taken together, this will look like:

def applyShift(text, shift):
  # Get our coder using buildCoder and shift
  coder = buildCoder(shift)
  # Now get our coded string using coder and text
  coded_text = applyCoder(text, coder)
  # We have our coded text!  Let's return it:
  return coded_text