How do I write a code for this in Python?

Question

1.00/5 (1 vote)

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Let the given string be “Python” and the key is 3 letters away from each letter of the alphabet
So “python” becomes “sbwkrq”

What I have tried:

Python

x=input()
for i in range(0,len(x)):
  if x[i]=='x':
    x.remove('x')
    x.insert(i,'a')
  if x[i]=='y':
    x.remove('y')
    x.insert(i,'b')
  if x[i]=='z':
    x.remove('z')
    x.insert(i,'c')
  else:
    x.del('x[i]')
    x.insert(i,chr(ord(x[i]+1)))
print(x)

Posted 8-Nov-20 20:39pm

Member 14987645

Updated 8-Nov-20 21:12pm

CPallini

v2

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CPallini · Accepted Answer · 2020-11-08T21:10:00

Solution 1

Just add 3 to ord(x[i]) and then check (and adjust) the out-of-range cases:

Python

x = input()
y = ''
for i in range(0,len(x)):
  c = ord(x[i]) + 3
  if c > ord('z'):
    c = c - ord('z') + ord('a') - 1
  y = y + chr(c)

print(y)

You can also do that using a one-liner expression

Python

x = input()
y = ''.join((chr((ord(l)-ord('a') + 3) % 26 + ord('a'))) for l in x)
print(y)

Posted 8-Nov-20 21:10pm

CPallini

Updated 8-Nov-20 21:19pm

v2

Comments

Richard MacCutchan 9-Nov-20 4:13am

Don't forget the upper case letters.

CPallini 9-Nov-20 4:16am

That is left as an exercise. :-)

OriginalGriff · Accepted Answer · 2020-11-08T21:13:00

Strings are immutable in Python, so you can't remove and insert characters.
Instead, do it like this:

Python

result = ''
offset = 3
for i in range(0,len(x)):
   val = ord(x[i]) + offset
   if val > ord('z'):
      val = val - 26
   result = result + chr(val)
print(result)

Using a variable to hold your offset means that your Caesar Cypher becomes more flexible, comparing to the last valid value means the wrap works regardless of the value of offset, provided it is positive.