How To Make Shift('w','f') Return 'b'?

Using this program to take out spaces, punctuation, and make letters lower case... def pre_process(s): #Enter: 'Jim's secret password.' s= s.replace(''','') s= s.replace('

Solution 1:

defshift(ch, k):
    returnchr(ord('a') + ((ord(ch) - ord('a')) + 
                           (ord(k) - ord('a'))) % 26)

Sort of an explanation:

defshift(ch, k):
    ## k_delta# ────>## ch_delta                 k_delta# ────────────────────────>────># a....f.........m....r....w..zab# ──────────────>────>         ┊# ch_delta       k_delta       ┊#                              ┊#                             %26

    ch_delta = ord(ch) - ord('a')
    k_delta = ord(k) - ord('a')
    returnchr(ord('a') + (ch_delta + k_delta) % 26)

Unless k varies, you can use str.translate to speed up encryption:

import string
message = 'mw'
key = 'f'
enc_table = string.maketrans(
    string.ascii_lowercase,
    ''.join(shift(c, key) for c instring.ascii_lowercase)
)
message.translate(enc_table) # -> 'rb'

I'd also suggest replacing the magic number26 with len(string.ascii_lowercase) for example.

Decryption can be done using the same function, but with a different key. The relation between them is that enc_delta + dec_delta = 0 modulo 26. From this results that dec_delta = -enc_delta % 26. Therefore:

dec_k = chr(ord('a') + ((ord(enc_k) - ord('a'))) % 26)

Solution 2:

You changed question.

Following to according to old question: How to make shift('w','f') return 'b'?

1. Get difference of second argument from the alpha a, code is diff = a2-start
2. Get next value from the first argument by adding difference, code is next = a1+diff
3. Check next value is greater then alpha z or not.
4. If not greater then z then new value is next value.
5. If greater then get new value from alpha a
6. Return value character.

code:

def shift(ch,k):
    start = ord("a")
    end = ord("z")
    a1 = ord(ch)
    a2 = ord(k)

    diff = a2-start
    print"\ndiff:", diff
    next = a1+diff
    print"next value:", nextifnext>end:
        new = next-end-1print"new1:", new
        new = start + new  
    else:
        new = nextprint"new value:", new

    returnchr(new)


rs = shift("w", "f")
print"w and f:", rs

rs = shift("e", "b")
print"e and b:", rs

rs = shift("z", "b")
print"z and b:", rs

rs = shift("x", "b")
print"x and b:", rs

output:

vivek@vivek:~/Desktop/stackoverflow$ python 26.py 

diff: 5
next value: 124
new1: 1
new value: 98
w andf: b

diff: 1
next value: 102
new value: 102
e andb: f

diff: 1
next value: 123
new1: 0
new value: 97
z andb: a

diff: 1
next value: 121
new value: 121
x andb: y
vivek@vivek:~/D

Solution 3:

Decrytion/Encryption Python

code:

def shift(ch, k):
    returnchr(ord('a') + ((ord(ch) - ord('a')) + (ord(k) - ord('a'))) % 26)


def reshift(ch, k):
    tmp =  (ord(ch) - (ord(k) - ord('a')))
    if tmp<ord('a'):
        tmp = ord("a") +(26 - (ord("a") - tmp))
    returnchr(tmp)

print"w and f:"
re = shift("w", "f")
print"Encryption:", re
re = reshift(re, "f")
print"Decrytion:", re

print"----------"print"e and b"
re = shift("e", "b")
print"Encryption:", re
re = reshift(re, "b")
print"Decrytion:", re

print"----------"print"z and b"
re = shift("z", "b")
print"Encryption:", re
re = reshift(re, "b")
print"Decrytion:", re

print"----------"print"x and b"
re = shift("x", "b")
print"Encryption:", re
re = reshift(re, "b")
print"Decrytion:", re

output:

vivek@vivek:~/Desktop/stackoverflow$ python 26.py 
w andf:Encryption: b
Decrytion: w
----------
e and b
Encryption: f
Decrytion: e
----------
z and b
Encryption: a
Decrytion: z
----------
x and b
Encryption: y
Decrytion: x
vivek@vivek:~/Desktop/stackoverflow$