function.py

a=2
b=3
c=1
print('sum=',a+b+c)
# function:to add 3 numbers
sum=0
def add(a,b,c):
    sum=a+b+c
    print('sum of 3 numbers:',sum)
n1=int(input("enter first number"))
n2=int(input("enter second number"))
n3=int(input("enter third number"))
add(n1,n2,n3)
#write a program to find factorial of a number,using recursion
# using function with for a loop
def fac(n):
    fact=1
    for i in range(1,n+1):
        fact=fact*i
    print("factorial of the number is:",fact)

n1=int(input("enter a number"))
fac(n1)
# using while loop

def factorial(n1):
     if n1 < 0 :
         print("0")
     elif n1==0 or n1==1:
         print("1")
     else:
         fact=1

         while(n1>1):
             fact=fact*n1
             n1=n1-1
         print("factorial of the number is:",fact)
a1=int(input("enter a number"))
factorial(a1)

#write a program to make a simple calculator add,sub,mul,div,mod
sum=0
def add(a,b):
    sum=a+b
    print("sum of the numbers:",sum)
sub=0
def sub(a,b):
    sub=a-b
    print("sub of the number is",sub)
mul=0
def mul(a,b):
    mul=a*b
    print("mul of the number is",mul)
div=0
def div(a,b):
    div=a/b
    print("division of the number is",div)

n1=int(input("enter the first number"))
n2=int(input("enter the first number"))
print("1.add\n2.sub\n3.mul\n4.div")
choice=int(input("enter your selection"))
if choice==1:
    add(n1,n2)
elif choice==2:
    sub(n1,n2)
elif choice==3:
    mul(n1,n2)
elif choice==4:
    div(n1,n2)
else:
    print("invalid")