shifting letters using ord and chr

Question

I am trying to do a function that shifts each letter in each word to the right by value and these words will be from a list that I will open it using "open"function I wrote the code, and I am facing some difficulties here here is my code

def test():
value=eval(input("Value here!"))
with open ("word-text.txt","r") as f:
    for ord in (f):
        print (ord)
        for chr in ord:
            print (chr)
            #nice=(chr[len(ord)+value])
        ''.join([chr(ord(i)+2) for i in s])
        print (i)

this is the output I get

Value here!2
apples

a
p
p
l
e
s


Traceback (most recent call last):
  File "<pyshell#54>", line 1, in <module>
    test()
  File "/Users/user/Desktop/Outlook(1)/lab6.py", line 59, in test
    ''.join([chr(ord(i)+2) for i in s])
NameError: global name 's' is not defined

the list that I have the following words apples oranges watermelon kiwi zucchini carrot okra jalapeno pepper cucumber banana and when I use this code

ef test():
value=eval(input("Value here!"))
with open ("word-text.txt","r") as f:
    for ord in (f):
        print (ord)
        for chr in ord:
            print (chr)
            nice=(chr[len(ord)+value])
            print (nice)

I get this output

Value here!2
apples

a
Traceback (most recent call last):
  File "<pyshell#56>", line 1, in <module>
    test()
  File "/Users/user/Desktop/Outlook(1)/lab6.py", line 58, in test
    nice=(chr[len(ord)+value])
IndexError: string index out of range
>>> 

What am I doing wrong here? and which code is best to use, to get it working

Thanks

Answer 1

While your approach is generally on a somewhat right track, there are some problems with it as others have noted. Since it seems that you're having trouble understanding what to do and how to go about solving the problem, I've tidied your code (made a few edits here and there) and heavily documented my edit of your code so you can understand what the approach should be:

def test():
    value=input("Value here!") #eval is bad AND dangerous practice. Avoid using it.
    with open ("word-text.txt","r") as f:
        #At this point you can do one of two things:
        #1) read the entire file line by line
        #2) read the entire file into a list, and loop/iterate over that list
        #In this example, I'll read the file line by line:
        nice_strings = []
        for line in f:
            line = line.strip() #remove any extraneous whitespace from the line (e.g. spaces and newlines)
            nice_str_chars = []
            #At this point, you want to read EACH character in the line
            #N.B.: ord is the name of a built-in function. Use another name like `char` (below):
            for char in line:
                #Since you're in this loop, you are dealing with EACH individual character of each line
                #And, as you want to "shift" the character by some number of places
                #Python doesn't allow you to natively shift strings by arbitrary amounts,
                #so, the only way we can do so is to convert EACH character into its numeric representation.
                #In order to do so, you have to use the `ord` function which converts characters into
                #their respective integer representation.
                int_of_char = ord(char)
                #At this point, the character has been converted to it's integer equivalent
                #NOW, you can "shift" it. In other words, add the value to the `int_of_char`:
                int_of_char += value #update the value of the variable
                #At this point, the value has been modified, and the INTEGER value of the character has been
                #shifted. However, we don't want the shifted INTEGER value: we want the shifted CHARACTER value.
                #So, how do we convert integers to characters? Python has a builtin function called `chr` which
                #does exactly that.
                #So, let's convert the shifted INTEGER to a shifted CHARACTER using `chr`:
                nice_char = chr(int_of_char)
                #print it out the original and modified characters so you can see what's in the string (this step is optional)
                print char, '=>', nice_char
                #At this point we've successfully shifted the character. However, since this is just A character of the original
                #string, we need a way to save the updated characters as a string. There are a number of ways to do this.
                #For simplicity, we can use a list `nice_str_chars`:
                nice_str_chars.append(nice_char)
            #At this point we've looped over all the characters in ONE LINE, and we've calculated and stored the shifted
            #characters for that same line. However, since we've stored the characters in a list: `nice_str_chars`, we
            #have to convert it to a string. We can do that using the `join` method on an empty string, with 
            #`nice_str_chars` as the list (as we want to join the characters of the list into a string):
            nice_str = ''.join(nice_str_chars)
            #And, since you want to shift ALL the lines, you ought to append the corrected line to a list that can later be
            #returned:
            nice_strings.append(nice_str)
            #you can print it out if necessary:
            print line, '=>', nice_str, '\n'
        #At this point, you've successfully looped over the entire file, shifted all lines by a user entered integer amount,
        #now, all you have to do is return it, or do something else with them (i.e. write the updated strings to another file).
        #That part, I'll leave up to you.
        return nice_strings

The only problem with this approach is that it is not circular (i.e. - it doesn't loop back around: e.g. z shifted by 3 does not become c), as the values will exceed the upper bound of their respective character set (as revealed in the OUTPUT section below). And, if the value entered is very large (i.e. greater than the bounds of the character set in which you're working, you'll get gibberish.

However, I don't know if that's a requirement of your problem (which may not be as you're basically doing a primitive encryption of passwords as suggested by your previous questions), but I thought that I'd mention in nonetheless.

OUTPUT:

Value here!2
a => c
p => r
p => r
l => n
e => g
s => u
apples => crrngu 

o => q
r => t
a => c
n => p
g => i
e => g
s => u
oranges => qtcpigu 

w => y
a => c
t => v
e => g
r => t
m => o
e => g
l => n
o => q
n => p
watermelon => ycvgtognqp 

k => m
i => k
w => y
i => k
kiwi => mkyk 

z => |
u => w
c => e
c => e
h => j
i => k
n => p
i => k
zucchini => |weejkpk 

c => e
a => c
r => t
r => t
o => q
t => v
carrot => ecttqv 

o => q
k => m
r => t
a => c
okra => qmtc 

j => l
a => c
l => n
a => c
p => r
e => g
n => p
o => q
jalapeno => lcncrgpq 

p => r
e => g
p => r
p => r
e => g
r => t
pepper => rgrrgt 

c => e
u => w
c => e
u => w
m => o
b => d
e => g
r => t
cucumber => ewewodgt 

b => d
a => c
n => p
a => c
n => p
a => c
banana => dcpcpc