Write a program to find the sum of natural numbers - Python

[ Write a program to find the sum of natural numbers ]

write a program to find the sum of natural numbers

num = int(input("Enter a number: "))  

if num < 0:  
   print("Enter a positive number")  
else:  
   sum = 0  
   # use while loop to iterate un till zero  
   while(num > 0):  
       sum += num  
       num -= 1  
   print("The sum is",sum)  

write a program to find LCM

def lcm(x, y):  
   if x > y:  
       greater = x  
   else:  
       greater = y  
  while(True):  
       if((greater % x == 0) and (greater % y == 0)):  
           lcm = greater  
           break  
       greater += 1  
   return lcm  


num1 = int(input("Enter first number: "))  
num2 = int(input("Enter second number: "))  
print("The L.C.M. of", num1,"and", num2,"is", lcm(num1, num2)) 

write a program to find HCF

def hcf(x, y):  
   if x > y:  
       smaller = y  
   else:  
       smaller = x  
   for i in range(1,smaller + 1):  
       if((x % i == 0) and (y % i == 0)):  
           hcf = i  
   return hcf  

num1 = int(input("Enter first number: "))  
num2 = int(input("Enter second number: "))  
print("The H.C.F. of", num1,"and", num2,"is", hcf(num1, num2))  

write a program to convert decimal to binary, octal and hexadecimal

dec = int(input("Enter a decimal number: "))  

print(bin(dec),"in binary.")  
print(oct(dec),"in octal.")  
print(hex(dec),"in hexadecimal."  

python program to find ascii value of a character

c = input("Enter a character: ")  
print("The ASCII value of '" + c + "' is",ord(c))

write a program to make a simple calculator

# define functions  
def add(x, y):  
   """This function adds two numbers"""
   return x + y 
def subtract(x, y): 
   """This function subtracts two numbers""" 
   return x - y 
def multiply(x, y): 
   """This function multiplies two numbers""" 
   return x * y 
def divide(x, y): 
   """This function divides two numbers"""  
   return x / y  
# take input from the user  
print("Select operation.")  
print("1.Add")  
print("2.Subtract")  
print("3.Multiply")  
print("4.Divide")  

choice = input("Enter choice(1/2/3/4):")  

num1 = int(input("Enter first number: "))  
num2 = int(input("Enter second number: "))  

if choice == '1':  
   print(num1,"+",num2,"=", add(num1,num2))  

elif choice == '2':  
   print(num1,"-",num2,"=", subtract(num1,num2))  

elif choice == '3':  
   print(num1,"*",num2,"=", multiply(num1,num2))  
elif choice == '4':  
   print(num1,"/",num2,"=", divide(num1,num2))  
else:  
   print("Invalid input")    

write a program to sort words in alphabetic order

my_str = input("Enter a string: ")  
# breakdown the string into a list of words  
words = my_str.split()  
# sort the list  
words.sort()  
# display the sorted words  
for word in words:  
   print(word)  

write a program to print the elements of an array present on even position

arr = [1, 2, 3, 4, 5];     

print("Elements of given array present on even position: ");    

for i in range(1, len(arr), 2):    
    print(arr[i]);