30.Example Programs using Strings

Remove all vowel characters from a string( university question)

vowels="AEIOUaeiou"
s=input("Enter the string...")
ns=""
for char in s:
    if char not in vowels:
        ns=ns+char
print("new string after removing vowels=",ns)

Remove characters at odd index positions from a string ( university question)

s=input("Enter the string..:")

i=0

ns=""

while i<len(s):

    if i%2==0:

        ns=ns+s[i]

    i=i+1

print("New string:",ns)

palindrome checking without reversing the string ( university question)
s=input("Enter the string...")
if s==s[::-1]:
    print("palindrome..")
else:
    print("not palindrome...")

Palindrome checking using loop

s=input("Enter the string..")

beg=0

end=len(s)-1

while beg<end:

   if s[beg]!=s[end]:

         print("Not palindrome")

         break

   beg+=1

   end-=1

else:

  print("Palindrome")

Replace all the spaces in the input string with * or if no spaces found,put $ at the start and end of the string.(university question)

s=input("Enter the string:")
s=s.replace(" ","*")
if "*" not in s:
    s="\$"+ s +"\$"
    print(s)
else:
    print(s)

Slice the string to two separate strings; one with all the characters in the odd indices and one with all characters in even indices.(university question)

s=input("enter the string:")

eps=s[0:len(s):2]

print("slice with even position characters:",eps)

ops=s[1:len(s):2]

print("slice with odd position chracters:",ops)

Binary to Decimal conversion

bitstring=input("Enter a binary number...")

decno=0
expnt=len(bitstring)-1
for bit in bitstring:
    decno=decno+int(bit)* 2 ** expnt
    expnt=expnt-1
print ("The decimal number is=", decno)

Decimal to Binary Conversion

decno=int(input("Enter the decimal number...."))
if decno==0:
    print("The binary equivalent is....0000")
else:
    binaryno=""
    while decno!=0:
        b=decno%2
        binaryno=str(b)+binaryno
        decno=decno//2
    print("The binary equivalent is....",binaryno)

Remove all occurrence of a substring from a string

s=input("enter the string..")

ss=input("enter substring to remove..")

ls=len(s) # length of the string

lss=len(ss) # length of the substring

ns="" # new string

i=0

while i<ls:

  css=s[i:lss+i] #css is the substring to be compared extracted from main string

  if css==ss:

    i=i+lss

  else:

    ns=ns+s[i]

    i=i+1

print("new string",ns)

The above program can also be written with built in function replace()

str=input("Enter string ..")

sstr=input("Enter the substring to remove..")

nstr=str.replace(sstr,"")

print("string after removing substring..",nstr)

Converting all lowercase letters into uppercase ( university question)

import string

s=input('Enter the string...')

ns=""

for c in s:

 if c in string.ascii_lowercase:

    c=chr(ord(c)-32)

 ns=ns+c

print("new string=",ns)

Swapping case ..small letters to capital letters and capital letters to small letters.

s=input('Enter the string...')

ns=""

sletter='abcdefghijklmnopqrstuvwxyz'

cletter='ABCDEFGHIJKLMNOPQRSTUVWXYZ'

for c in s:

  if c in sletter:

     c=chr(ord(c)-32)

  elif c in cletter:

    c=chr(ord(c)+32)

  ns=ns+c

print("new string=",ns)

Program to replace all occurrence of a substring with a new substring (university question)

s=input("enter string..")

ss=input("enter substring to remove..")

nss=input("enter the substring to replace....")

ls=len(s)

lss=len(ss)

ns=""

i=0

while i<ls:

  css=s[i:lss+i]

  if css==ss:

     ns=ns+nss

     i=i+lss

  else:

     ns=ns+s[i]

     i=i+1

print("new string",ns)

Reversing the first and second half of a string separately ( university question)

s=input("Enter the string..:")

l=len(s)

fs=s[0:l//2]

ss=s[l//2:]

fs=fs[::-1]

ss=ss[::-1]

s=fs+ss

print("New string after reversal:::",s)

Encrypt a string using the shift cipher( key=3 Ceaser cipher)

import string
plaintxt=input("enter plain text in small letters..")
k=int(input("Enter the key...."))
s=string.ascii_lowercase
ciphertxt=""

for c in plaintxt:
    i=s.find(c)
    if i!=-1:
        ni=(i+k) % 26
        ciphertxt=ciphertxt+s[ni]
    else:
        ciphertxt=ciphertxt+c
print("cipher text...",ciphertxt)

Write a Python program to check the validity of a password given by the

user.

The Password should satisfy the following criteria:

1. Contains at least one letter between a and z

2. Contains at least one number between 0 and 9

3. Contains at least one letter between A and Z

4. Contains at least one special character from $, #, @

Minimum length of password: 6

import getpass

dig='0123456789'

cl="ABCDEFGHIJKLMNOPQRSTUVWXYZ"

sl="abcdefghijklmnopqrstuvwxyz"

sc="$#@"

flag1=0;flag2=0;flag3=0;flag4=0;flag5=0

password=getpass.getpass()

if len(password)>=6:

    flag5=1

for c in password:

        if c in dig:

            flag2=1

        if c in sl:

            flag1=1

        if c in cl:

            flag3=1

        if c in sc:

            flag4=1

if flag1 and flag2 and flag3 and flag4 and flag5:

    print("Strong password")

else:

    print("Invalid password")

more simple code with any

# Program to check the validity of a password

password = input("Enter the password to validate: ")

# Criteria checks

has_lower = any(char.islower() for char in password)

has_upper = any(char.isupper() for char in password)

has_digit = any(char.isdigit() for char in password)

has_special = any(char in "$#@" for char in password)

is_long_enough = len(password) >= 6

# Validate the password

if has_lower and has_upper and has_digit and has_special and is_long_enough:

    print("The password is valid.")

else:

    print("The password is invalid. Please ensure it meets all the criteria.")

  

Write Python program to count the total number of vowels, consonants, digits and blanks in a string.(university question)

s = input('Enter the string:')
s = s.lower()
vowels = "aeiou"
consonants = "bcdfghjklmnpqrstvwxyz"
digits = "1234567890"
space = " "
c = 0
v = 0
d = 0
ws = 0
for i in s:
    if i in vowels:
        v+=1
    elif i in consonants:
        c+=1
    elif i in digits:
        d+=1
    elif i in space:
        ws+=1
print("Consonents={},Vowels={},Digits={},Spaces={}".format(c,v,d,ws))

Note: you can do this program using library functions

# Program to count vowels, consonants, digits, and blanks in a string

# Input string from the user

text = input("Enter a string: ")

# Initialize counters

vowel_count = 0

consonant_count = 0

digit_count = 0

blank_count = 0

# Define vowels

vowels = "aeiouAEIOU"

# Loop through each character in the string

for char in text:

    if char.isdigit():  # Check if the character is a digit

        digit_count += 1

    elif char.isspace():  # Check if the character is a blank space

        blank_count += 1

    elif char.isalpha():  # Check if the character is an alphabet

        if char in vowels:  # Check if the character is a vowel

            vowel_count += 1

        else:  # If it's an alphabet but not a vowel, it's a consonant

            consonant_count += 1

# Output the results

print("Total vowels:", vowel_count)

print("Total consonants:", consonant_count)

print("Total digits:", digit_count)

print("Total blanks:", blank_count)

Count number of letters , digits, words,uppercase and lower case letters in a string

num_letters = 0

num_digits = 0

num_words = 0

num_uppercase = 0

num_lowercase = 0

input_string = input("Enter a string: ")

for char in input_string:

    if char.isalpha():

        num_letters += 1

    if char.islower():

        num_lowercase += 1

    elif char.isupper():

         num_uppercase += 1

    elif char.isdigit():

        num_digits += 1

# Count words

words = input_string.split()

num_words = len(words)

    

print("Number of letters:", num_letters)

print("Number of digits:", num_digits)

print("Number of words:", num_words)

print("Number of uppercase letters:",num_uppercase)

print("Number of lowercase letters:",num_lowercase)

Assume that the variable data refers to the string "Python rules!". Use a string method to perform the following tasks: ( University Question)

a. Obtain a list of the words in the string.

b. Convert the string to uppercase.

c. Locate the position of the string "rules" .

d. Replace the exclamation point with a question mark.

data="Python rules!"

words=data.split(" ")

for w in words:

    print(w)

    

data=data.upper()

print(data)

pos=data.index('rules')

print(pos)

data=data.replace('!','?')

print(data)

Write a Python program to get a string and change all occurrences of its first character to '$', except the first character itself.(university question)

Example:onion  will change to oni$n.

def change_first_char_occurrences(input_string):

    # Check if the string is not empty

    if input_string:

        first_char = input_string[0]

        # Replace all occurrences of the first character (excluding the first one) with '$'

        modified_string = first_char + input_string[1:].replace(first_char, '$')

        return modified_string

    return input_string  # Return the original string if it's empty

# Get input from the user

user_input = input("Enter a string: ")

# Call the function and print the result

result = change_first_char_occurrences(user_input)

print("Modified string:", result)

Output:

Enter a string: onion

Modified string: oni$n

Give the input "12345", write a python code snippet to check if it is numeric.(university question)

input_value = "12345"

# Check if the input is numeric

if input_value.isnumeric():

    print(f"The input '{input_value}' is numeric.")

else:

    print(f"The input '{input_value}' is not numeric.")

You are working on a text processing application for a content moderation team. The team needs a feature to analyse user generated sentences and recognize their characters for better readability and analysis. Specifically they want all capital letters to appear first, followed by small letters, then digits and finally any special characters. Write a python program to implement this feature ensuring the reorganised output is displayed as a single word. ( university question)

def reorganize_characters(sentence):

    # Separate characters into categories

    uppercase = ""

    lowercase = ""

    digits = ""

    specials = ""

    for char in sentence:

        if char.isupper():

            uppercase=uppercase+char

        elif char.islower():

            lowercase=lowercase+char

        elif char.isdigit():

            digits=digits+char

        else:

            specials=specials+char

    # Combine the characters in the desired order

    result = uppercase+ " " +lowercase+" "+digits+" "+specials

    return result

# Input sentence

user_input = input("Enter a sentence: ")

# Get the reorganized output

output = reorganize_characters(user_input)

# Display the result

print("Reorganized Output:", output)