if i write an if statement with an elif, do I always have to put an else statement? code example

Example 1: if and elif

'''In this program, we input a number
check if the number is positive or
negative or zero and display
an appropriate message
This time we use nested if statement'''

num = float(input("Enter a number: "))
if num >= 0:
    if num == 0:
        print("Zero")
    else:
        print("Positive number")
else:
    print("Negative number")

Example 2: if and elif

if test expression:
    Body of if
elif test expression:
    Body of elif
else: 
    Body of else