Btukfyl

A text is divided in groups with seven letters. Each group is scrambled with the key 6015423 (letter with index 0 on index 6, letter with index 1 on index 0, letter with index 2 on index 1...).

Instead of the correct word "serpent" (tried it only with the first seven-letter group, the same problem occurs when %7 is left out) my code yields a false result beginning with index 4: serpsne.

What is the mistake?

list=['e','r','n','t','e','p','s']

clear=

for x in list:    

    if list.index(x)%7==0:

        a=list[list.index(x)+6]

    elif list.index(x)%7==1:

        a=list[list.index(x)-1]

    elif list.index(x)%7==2:

        a=list[list.index(x)-1]

    elif list.index(x)%7==3:

        a=list[list.index(x)+2]

    elif list.index(x)%7==4:

        a=x

    elif list.index(x)%7==5:

        a=list[list.index(x)-3]

    else:               

        a=list[list.index(x)-6]

    clear.append(a)

clear=''.join(clear)

print(clear)

(Don´t know why this box inserts two blank lines after for and else, my code has no blank lines.)

Not sure why you're doing this much! Try this one below:

lst=['e','r','n','t','e','p','s']

clear=

key='6015423'

for x in key:

    clear.append(lst[int(x)])



clear=''.join(clear)

print(clear)

Because list.index('e') is always 0.

It will find the index of the first occurence of 'e', not the second one and hence it will never execute this:

elif list.index(x)%7==4:

    a=x

Try to run this code:

list=['e','r','n','t','e','p','s']

for x in list:

print ( list.index(x))

You will get 0123056 instead of 0123456