Game Development Reference
In-Depth Information
the value of
num
here would be the character
'^'
(The ordinal of
'^'
is
94
). But ^ isn't
a letter at all. We wanted the ciphertext to "wrap around" to the beginning of the alphabet.
The way we can do this is to check if
key
has a value larger than the largest possible
letter's ASCII value (which is a capital "Z"). If so, then we want to
subtract
26
(because
there are 26 letters in total) from
num
. After doing this, the value of
num
is
68
, which is
the ASCII value for
'D'
.
41. elif symbol.islower():
42. if num > ord('z'):
43. num -= 26
44. elif num < ord('a'):
45. num += 26
If the symbol is a lowercase letter, the program runs code that is very similar to lines 36
through 40. The only difference is that we use
ord('z')
and
ord('a')
instead of
ord
('Z')
and
ord('A')
.
If we were in decrypting mode, then
key
would be negative. Then we would have the
special case where
num -= 26
might be less than the smallest possible value (which is
ord('A')
, that is,
65
). If this is the case, we want to
add
26
to
num
to have it "wrap
around".
47. translated += chr(num)
48. else:
49. translated += symbol
The
translated
string will be appended with the encrypted/decrypted character. If
the symbol was not an uppercase or lowercase letter, then the else-block on line 48 would
have executed instead. All the code in the else-block does is append the original symbol to
the
translated
string. This means that spaces, numbers, punctuation marks, and other
characters will not be encrypted (or decrypted).
50. return translated
The last line in the
getTranslatedMessage()
function returns the translated
string.
The Start of the Program
52. mode = getMode()
53. message = getMessage()
54. key = getKey()
