Rotating letters by a fixed number of places [python programming]

Question

I am new to python programming and would like to write a program which has the following requirement:

The program accepts an input string and the number of rotations. Rotate all characters in the string and print the result on screen.

For example, input is ABCDZ 3 Then, output is DEFGC

def rotate(input,d): 

Rfirst = input[0 : len(input)-d] 
Rsecond = input[len(input)-d : ] 

print "Right Rotation : ", (Rsecond + Rfirst)

However, I have written a few codes by myself and turned out that I could only rotate the character within ABCDZ to e.g. ZABCD instead of the rotation pattern dictated in the requirement.

Would anyone like to give help on the issue? How should I start with the correct direction? Thank you very much to all of you. I am really frustrated..

Have a look at [`ord`](https://docs.python.org/3/library/functions.html#ord) and [`chr`](https://docs.python.org/3/library/functions.html#chr). — Christian König, Dec 07 '18 at 14:15
In your example you "shift" the letters, so a->d, b->e... In your code, you change positions of the letters in your input. Decide what you want to do. — Christian König, Dec 07 '18 at 14:24
What's the logic behind the conversion from `ABCDZ` to `ZABCD` ? — Pedro Lobito, Dec 07 '18 at 14:38

iGian · Answer 1 · 2018-12-07T14:48:31.360

0

Could this work?

def rotate_str(mstr, n):
  reverse = False
  if n < 0:
    n, reverse = - n, True
  for _ in range (0,n):
    if not reverse: mstr = mstr[-1] + mstr[0:-1]
    if reverse: mstr = mstr[1:] + mstr[0]
  return mstr

Negative n reverses the direction of rotation.

mstr = 'ABCDZ'
print(rotate_str(mstr, 3)) #=> CDZAB
print(rotate_str(mstr, -4)) #=> ZABCD

edited Dec 07 '18 at 14:48

answered Dec 07 '18 at 14:29

iGian

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Rotating letters by a fixed number of places [python programming]

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