ASCII encryption program in Python

Question

I have recently written a program that reads information from a CSV file and puts it into lists. An encryption sub procedure converts the characters to ASCII, adds 2 then converts them back to characters.

import csv

ifile = open("messages.csv","rb")
reader= csv.reader(ifile)

plain_text= []
plain_ascii= []
encrypted_ascii= []
encrypted_text= []
latitude= []
longitude= []

for row in reader:
    latitude.append(row[0])
    longitude.append(row[1])
    plain_text.append(row[2])

encrypted_text=[''.join(chr(ord(ch)+2) for ch in string) for string in 
plain_text]
print plain_text
print encrypted_text

count=0

print ""
while True:
    print ""
    response=int(raw_input("Enter 1 to see the next record, 2 to see the 
previous record or 3 to end the program:"))
    print""
    if response > 3 or response < 1:
        print ("Please respond with one of the set responses.")
    elif response == 3:
        print "Process ended"
        break
    else:
        if response==1:
            count += 1
            if count >= len(plain_text):
                count = 0
        elif response==2:
            count -= 1
            if count < 0:
                count = len(plain_text) - 1
        print ""
        print("Record {0}:".format(count))
        print ""
        print("Latitude: {0}  Longitude: {1}  Unencrypted Text: {2} 
Encrypted Text: {3}".format(latitude[count],longitude[count], 
plain_text[count], encrypted_text[count]))

ifile.close()

Is there any way to make the entirety of this much more precise or simpler, and possibly any way to restructure this?

Answer 1

Just a few notes about print, I see you're not using parenthesis so i'm guessing you're using python 2.x. I would urge you to switch to python 3.5+ now, as python 2.x is at end of life. However if you insist on using it

-Keep consistent on using parenthesis

-You can use \n inside the string to add a newline:

print "Hello World!\n"

If you switch to python 3.x you can use the print function and pass in the end parameter to append a new line after your string:

s = "Hello World!"
print(s, end='\n') #NOTE: @Coal_ points out this is the default
# so if you didn't want there to be a newline you'd have to overwrite
# print(s, end=' ')
# @Solomon, and if you wanted a space between your outputs,
# print(s, end='\n\n')

That way you don't have seemingly useless print statements everywhere.

Answer 2

response=int(raw_input("Enter 1 to see the next record, 2 to see the previous record or 3 to end the program:"))
print""
if response > 3 or response < 1:

When you're checking for failure, instead of asking "is it one of these cases that I've thought of that are bad", ask "Is it not one of the case that are good". Doing the former raises the issue of whether you've thought of everything that can go wrong. What if they enter a float? A string? Instead, do:

response = (raw_input("Enter 1 to see the next record, 2 to see the previous record or 3 to end the program:"))
if response not in ['1','2','3']:

You're not using integer properties of response; you're just checking whether it's equal to a comparison value, not doing math on it, so there's no need to convert to int. If you are going to convert, do it after you've checked whether the input is valid.

You can use modular arithematic to get rid of some if statements:

if response=='1':
        count += 1  
elif response=='2':
        count -= 1
count = count%len(plaint_text)