Python源代码：Note: working for negative shift numbers also

Note: if reverse shift then we do encode - decode message

Note: preserving spaces alsosmall_chars = [chr(item) for item in range(ord('a'), ord('z')+1)]

upper_chars = [item.upper() for item in small_chars]

def encode_chr(chr_item, is_upper_case):

'''

Cipher each chr_item.

'''

# setting orig and end order.

if is_upper_case:

orig_ord = ord('A')

end_ord = ord('Z')

else:

orig_ord = ord('a')

end_ord = ord('z')

# calculating shift

temp_ord = ord(chr_item)+shift

# calculating offset order with modulo.

# char is after end_ord, calculating offset

num_of_chars = 26

offset_ord = (temp_ord - end_ord - 1)%num_of_chars

return chr(orig_ord + offset_ord)

# enable while loop to repeat until status not 'y'

status = 'y'

while status == 'y':

# enter word to cipher.

word = raw_input("Word: ")

# enter char shift

shift = input("Shift: ")

print

# create cipher list variable

cipher = list()

# loop trough each char in word

for chr_item in word:

# encode just letters.

# replace non-alfa with underscore: "_"

if chr_item in upper_chars or chr_item in small_chars:

# set is_uppser_case to True for upper case chars.

is_upper_case = (chr_item in upper_chars) and True

# cipher char.

temp_chr = encode_chr(chr_item, is_upper_case)

# append ciphered char to list

cipher.append(temp_chr)

elif chr_item is ' ':

cipher.append(chr_item)

else:

cipher.append('_')

# print word

print word

# print ciphered word

print ''.join(cipher)

# repeat again for another word?

status = raw_input("Repeat? [y|n]: ")

print

测试用例：

^{pr2}$

输出：Note: if reverse shift then we do encode - decode message>>>

Word: "Mary Had a Little Lamb"

Shift: 1

"Mary Had a Little Lamb"

_Nbsz Ibe b Mjuumf Mbnc_

Repeat? [y|n]: y

Word: _Nbsz Ibe b Mjuumf Mbnc_

Shift: -1

_Nbsz Ibe b Mjuumf Mbnc_

_Mary Had a Little Lamb_

Repeat? [y|n]: n

>>>