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Python Message Cipher Indexation Error + WhiteSpace issue

I am working on an exercise to encode a message in Python. The following function is supposed to take in a message and a number to shift the letters in each word by that amount in the alphabet i.e. the letter a if moved 3 spaced would become d.
I have two issues:
The length of the alphabet is only 26 characters long. If you shift a letter too far right i.e. past the 26th position of Z you get the following error:
IndexError: string index out of range
I'd be happy with a fix that shifts the index back to the start again and moves the letter index based on the remainder of whatever goes past 26 characters i.e. if there is a shift of 9 with the char y then the remaining 9 after 26 could be positioned start from a again, making y the letter i.
If I were to input a message with spaces i.e. "I need help", the returned characters do not retain the original white space between each word.
Can anyone help with questions 1 or 2?
def message_to_code():
normal_message = input(str("Please enter a message you would like coded: "))
Cipher_shift = int(input("Please enter the whole number you would like to act as the key to hide your message "))
Alphabet = "abcdefghijklmnopqrstuvwxyz"
Cipher_message = ' '
for letter in normal_message:
Encrypted_letter = Alphabet.find(letter) + Cipher_shift
Cipher_message = Cipher_message + Alphabet[Encrypted_letter]
return print(Cipher_message)
message_to_code()

Your first problem can be easily fixed by checking if Alphabet.find(letter) + Cipher_shift >= len(Alphabet). If it is, than Encrypted_letter = Encrypted_letter - len(Alphabet).
Your second problem was tricky to completely understand, but I think the fix you are looking for is checking if letter is a space. If it is, loop to the next character, if it's not, do the logic with that character.
The bug fixes look like this:
def message_to_code():
normal_message = input(str("Please enter a message you would like coded: "))
Cipher_shift = int(input("Please enter the whole number you would like to act as the key to hide your message "))
Alphabet = "abcdefghijklmnopqrstuvwxyz"
Cipher_message = ' '
for letter in normal_message:
if letter != ' ':
Encrypted_letter = Alphabet.find(letter) + Cipher_shift
if Encrypted_letter >= len(Alphabet):
Encrypted_letter -= len(Alphabet)
Cipher_message = Cipher_message + Alphabet[Encrypted_letter]
else:
Cipher_message += ' '
I also fixed some other problems. For example, if you have a capital letter, your original code wouldn't catch that, since Alphabet is only filled with lower-case letters. To fix this, I added a second array dedicated to capital-letters, and check to see if letter is capital or not.
The second fix is checking if letter is a part of the alphabet or not. If it isn't, that would mean letter is: '/', '.', ',', ':', ';', etc. If it does happen to be one of these characters, it just adds its original self to the encrypted string.
The modified code looks like this:
def message_to_code():
normal_message = input(str("Please enter a message you would like coded: "))
Cipher_shift = int(input("Please enter the whole number you would like to act as the key to hide your message "))
Alphabet = "abcdefghijklmnopqrstuvwxyz"
AlphabetCaps = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
Cipher_message = ""
is_letter = True
for letter in normal_message:
if letter != ' ':
if Alphabet.find(letter) != -1:
Encrypted_letter = Alphabet.find(letter) + Cipher_shift
is_letter = True
elif AlphabetCaps.find(letter) != -1:
Encrypted_letter = AlphabetCaps.find(letter) + Cipher_shift
is_letter = True
else:
is_letter = False
if is_letter:
if Encrypted_letter >= len(Alphabet):
Encrypted_letter -= len(Alphabet)
if Alphabet.find(letter) != -1:
Cipher_message += Alphabet[Encrypted_letter]
else:
Cipher_message += AlphabetCaps[Encrypted_letter]
else:
Cipher_message += letter
else:
Cipher_message += ' '
return print(Cipher_message)

How to find duplicate character in a string and increase its occurence after that character in Python?

I have written a program to find the duplicate character of a string, as below:
string = "India";
print("Duplicate characters in a given string: ");
#Counts each character present in the string
for i in range(0, len(string)):
count = 1;
for j in range(i+1, len(string)):
if(string[i] == string[j] and string[i] != ' '):
count = count + 1;
#Set string[j] to 0 to avoid printing visited character
string = string[:j] + '0' + string[j+1:];
#A character is considered as duplicate if count is greater than 1
if(count > 1 and string[i] != '0'):
print(string[i]);
But thats not it I just want to increase the duplicate character by putting one extra occurence of that character.
For Example:
input : "India"(Here Duplicate Character is 'i')
output : "IIndiia"(Increase one occurrence of the duplicate character)
Can any one help me in solving this?

Collect all counts in one go, and do so case-insensitively:
from collections import Counter
string = "India"
c = Counter(string.lower())
"".join(x * (1 + (c[x.lower()] > 1)) for x in string)
'IIndiia'

One easy way is to use standard python string methods:
line = "some string"
result = ""
for letter in line:
result = result + letter
if line.upper().count(letter.upper()) > 1:
result = result + letter

How do you split duplicate letters with "x" in Python?

I am trying to create a function which is able to detect when two letters back to back are duplicates, for example the ls in "hello", and split the duplicate letters with the letter "x". Here is my code:
plaintext = input("Enter plaintext here: ")
plaintext = plaintext.lower() # makes plaintext lowercase
plaintext = plaintext.replace(" ", "") # removes all spaces
# this separates all duplicate letters
i = 0 # sets i to 0
for letter in plaintext:
if plaintext[-1] == plaintext[-2]: # if the last letter is the same as the second to last
plaintext = plaintext[:-1] + "x" + plaintext[-1:] # separate them with an x
elif plaintext[i] == plaintext [i+1]: # if one letter is the same as the next letter
# the line above makes an error
plaintext = plaintext[:i+1] + "x" + plaintext[i+1:] #separate them with an x
i += 1
else:
i += 1
This code works when I enter hello there as the input; I receive helxlothere. However, when I test another input, such as heythere, IndexError: string index out of range shows up for elif line (line 12). How can I make this code work for all inputs?

You can use regex to achieve this.
For both approaches, it will work for hello there hey there
The difference comes when more than two character repetition happens.
approach 1
import re
string='hello there'
# find Any repeated character and add x in between them
answer = re.sub(r'(.)\1{1}', r'\1x\1', string)
print(answer)
Here for hellllo there text, you will get output helxllxlo there
approach 2
alternatively, you can use this method.
s="hello there"
for match in re.finditer(r"(.)\1+", s):
old=s[match.start():match.end()]
s=s.replace(old,'x'.join(old))
print(s)
here for hellllo there text, you will get output helxlxlxlo there as output.
I think the second approach will be more appropriate.

The IndexError is caused by the fact that you are looking at plaintext[i+1]. As you can see in the word heythere, there are no letters which match back to back, and therefore the code continues until it hits the end, and so you get an IndexError because there is no element i+1.
You can fix this by using this code instead:
plaintext = input("Enter plaintext here: ")
plaintext = plaintext.lower() # makes plaintext lowercase
plaintext = plaintext.replace(" ", "") # removes all spaces
# this separates all duplicate letters
i = 0 # sets i to 0
for letter in plaintext:
if plaintext[-1] == plaintext[-2]: # if the last letter is the same as the second to last
plaintext = plaintext[:-1] + "x" + plaintext[-1:] # separate them with an x
try:
elif plaintext[i] == plaintext [i+1]: # if one letter is the same as the next letter
# the line above makes an error
plaintext = plaintext[:i+1] + "x" + plaintext[i+1:] #separate them with an x
i += 1
else:
i += 1
except IndexError:
pass
This code should stop your code from crashing in the elif statement, while also completing properly.
Hope this helps, have a nice day!

You are receiving the IndexError because during iterating, when the loop reaches the last letter,
elif plaintext[i] == plaintext [i+1]:
this line checks for the letter after the last letter, which does not exist, which causes the program to run into IndexError.
You have to check till the second last letter, for it to work properly.

A simple and easier way to arrive at the same output with a bit easier logic.
Logic
Create a new string and insert all letters which are in the old string, plaintext, to the new string, newPlainText, and check only for one condition that is whether the last letter is same as current or not and if yes then also insert letter 'x' into the newPlainText and that's it!
plaintext = input("Enter plaintext here: ")
plaintext = plaintext.lower() # makes plaintext lowercase
plaintext = plaintext.replace(" ", "") # removes all spaces
# this separates all duplicate letters
newPlainText = plaintext[0] # copy the first letter of plaintext to the new string which will handle the duplicates and insert `x` between them
i = 1 # sets i to 1
while i < len(plaintext):
if plaintext[i] == plaintext[i-1]: # we check that if prev and current letters are same then also append x to the new string
newPlainText += "x"
newPlainText += plaintext[i] # we insert the required current letter to the new string in each iteration
i += 1
print(newPlainText)

Where is my logical error in this python script for capitalizing first letters of a sentence when there are multiple sentences?

I have a logical error I can't find. I am trying to capitalize the first letter of each sentence. I am having trouble understanding how to move on to the next sentence to capitalize the first letter. How do I move to the next sentence? If you see my error can you please tell me what it is?
def main():
# get a string from the user
stringAsked = input('Please enter a short statement consisting of a couple or more sentences ')
# call the capitalize function
modifiedString = capitalize(stringAsked)
# Print the string
print(modifiedString)
def capitalize(my_string):
# Initialize string and counter variables
modString = ''
ind = 0
# Create while loop to cycle through each character of the string
while ind < len(my_string):
# Assign Current character to the ch variable
ch = my_string[ind]
# If first character of string
if ind == 0:
# Store capitalized character in return variable
modString += ch.upper()
# Check if the character is at the end of the string
elif ch == '.' or ch == '!' or ch == '?':
# add current character to the return variable
modString += ch
# If more than one sentence
if ind + 2 < len(my_string):
# Add the space
modString += my_string[ind + 1]
# Capitalize the first character
modString += my_string[ind + 2].upper()
# Increment the index
ind = ind + 2
# If the character is in the middle of a sentence
else:
#Add the character to return variable
modString += ch
#increment the index to go to next character
ind = ind + 1
# return the variable to calling function
return modString
main()

Your indentation of your code regarding what to do after "." may seem to be the issue. You need the handling of the space and character after a full stop (or similar) to be indented so it is executed inside the "." condition and not as another condition at the same level.
def main():
# get a string from the user
stringAsked = input('Please enter a short statement consisting of a couple or more sentences ')
# call the capitalize function
modifiedString = capitalize(stringAsked)
# Print the string
print(modifiedString)
def capitalize(my_string):
# Initialize string and counter variables
modString = ''
ind = 0
# Create while loop to cycle through each character of the string
while ind < len(my_string):
# Assign Current character to the ch variable
ch = my_string[ind]
# If first character of string
if ind == 0:
# Store capitalized character in return variable
modString += ch.upper()
# Check if the character is at the end of the string
elif ch == '.' or ch == '!' or ch == '?':
# add current character to the return variable
modString += ch
# If more than one sentence
if ind + 2 < len(my_string):
# Add the space
modString += my_string[ind + 1]
# Capitalize the first character
modString += my_string[ind + 2].upper()
# Increment the index
ind = ind + 2
# If the character is in the middle of a sentence
else:
#Add the character to return variable
modString += ch
#increment the index to go to next character
ind = ind + 1
# return the variable to calling function
return modString
main()
Hope this makes sense!

What about this - first split the string at every "." and then walk through every sentence and switch first letter to capital.
s = "hello world. please help me. can we do this simpler?"
stringlist = s.split(". ")
def first_char_upper(stringlist):
for i in range(0, len(stringlist)):
stringlist[i] = stringlist[i][0].upper() + stringlist[i][1:]
return stringlist
print(first_char_upper(stringlist))
Output: > ['Hello world', 'Please help me', 'Can we do this simpler?']

word separator for python coding [closed]

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So the question reads:
Write a program that accepts as input a sentence in which all of the words are run together but the first character of each word is uppercase. Convert the sentence to a string in which the words are separated by spaces and only the first word starts with an uppercase letter. For example the string "StopAndSmellTheRoses." would be converted to " Stop and smell the roses."
I am so confused this my code so far.
def main():
#User enters a sentence
my_string=input('enter a sentence: ')
print(my_string.capitalize())
main()

You can loop through the string and add a character each time to a result:
my_string = "StopAndSmellTheRoses"
i = 0
result = ""
for c in my_string:
if c.isupper() and i > 0:
result += " "
result += c.lower()
else:
result += c
i += 1
print result
We'll use c for each character as we walk through the string and we'll use i to keep track of the position in the string.
There are two possibilities: it's either an uppercase character (excluding the first one) or it's not.
In the first case we'll add a space and that character as lowercase to the result. This ensures a space is inserted before each uppercase character further in the sentence.
In the second case it's a lowercase character or the uppercase character at the beginning of the sentence. We don't have to do anything with these and we'll add it right away.
Lastly we add one to i whenever we're done with a character (i += 1) as this means we correctly know where we are in the sentence.

Welcome to SO!
One way to do this is to loop through your string, checking the chars one by one:
#You've learned how to iterate through something, right?
i = 0 #a counter
for c in my_string: #get the characters of my_string, one by one.
if c.isupper(): #check if it's in upper case
if i == 0: #if it's the first letter
new_string += c #let it be like the original
else:
new_string += ' '+.lower() #it's not the first letter,
#so add space, and lower the letter.
else:
new_string += c #else, only add the letter to the new string
i += 1
Edit added a double-check to see if it's the first letter of the sentence or not. Updated demo.
As an alternative to using a counter, you can also use the built-in function enumerate, which returns a tuple of index and values.
for i,c in enumerate(my_string): #get the characters of my_string, one by one.
if c.isupper(): #check if it's in upper case
if i == 0: #if it's the first letter
new_string += c #let it be like the original
else:
new_string += ' '+c.lower() #it's not the first letter,
#so add space, and lower the letter.
else:
new_string += c #else, only add the letter to the new string
Demo
>>> my_string = 'ImCool'
>>> new_string = ''
>>> i = 0 #a counter
>>> for c in my_string: #get the characters of my_string, one by one.
if c.isupper(): #check if it's in upper case
if i == 0: #if it's the first letter
new_string += c #let it be like the original
else:
new_string += ' '+.lower() #it's not the first letter,
#so add space, and lower the letter.
else:
new_string += c #else, only add the letter to the new string
i += 1
>>> new_string
'Im cool'
Hope this helps!

You'll need a bit of regex.
import re
split = re.findall(r'[A-Z][a-z\.]+', 'HelloThisIsMyString.')
You'll also need to join those together (inserting spaces)
' '.join(...)
and handle case conversions
' '.join(word.lower() for word in split)
(and as you already did, capitalize the first word)
' '.join(word.lower() for word in split).capitalize()

It appears that you are a little confused and this is to be expected if you are new to Python. I'm assuming you take input from the user as opposed to input for a function. Either way I would create a simple function that you could insert the users input into. The function below will accomplish what the problem asks.
def sentenceSplitter(sentence):
result = ""
for i, x in enumerate(sentence): #i is character index, x is the element
if i == 0:
result = result + x
elif x.isupper() == False: #if element is not uppercase, add it to the result
result = result + x
else: # Otherwise, add a space and lowercase the next letter
result = result + " " +x.lower()
return(result)
To reiterate, if you are looking to print out the sentence you would write this after the function:
def main():
#User enters a sentence
my_string=input('enter a sentence: ')
print(sentenceSplitter(my_string))
main()
If you are still confused feel free to ask any further questions.