How to loop ascii between ascci 32 and ascii 126 in python

Question

I am writing a Caesar cipher program and i need to keep my values within the range of 32 and 126 ( the printable ascii set) when it encrypts itself. so when it gets to 126 it loops back to 32

here is the code

print("enter sentence to encrypt:")
string = input()
print("Please enter positive offset value:")
value = int(input())
finalstring = [ord(c) for c in string]
finalstring[:] = [c + value for c in finalstring]
finalstring = ''.join(chr(i) for i in finalstring)

There are loads of [Python Caesar cipher questions](http://stackoverflow.com/search?q=[python]+caesar) here on Stack Overflow already. Did you search through them before posting? — Martijn Pieters, Apr 23 '13 at 07:51
http://stackoverflow.com/questions/1538935/caesars-cipher-using-python-could-use-a-little-help — Ofiris, Apr 23 '13 at 07:52

paxdiablo · Answer 1 · 2013-04-23T08:02:25.877

Assuming you have a variable v that you wish to add a to, and have it constrained to the range 32..126 inclusive, this should do:

v = (v - 32 + a) % (127 - 32) + 32

So, for example, when adding 3 to 125:

v = (125 - 32 + 3) % (127 - 32) + 32
  =       96       %    95      + 32
  =                1            + 32
  =                       33

More generally:

def addWithConstraint (loval, hival, val, plus):
    return (val - loval + plus) % (hival + 1 - loval) + loval

Do note however that some modulo operations may not do what you expect for negative numbers but you can get around that by ensuring that you're always adding a positive numbers. For example, you could insert at the start of that function something like:

while plus < 0:
    plus = plus + hival + 1 - loval

How to loop ascii between ascci 32 and ascii 126 in python

1 Answers1