1.3 Input and Variables

The input() function is used to take user input.  The following code snippet will prompt the user to enter their name, wait for the user to enter their name and press enter.  The value that the user enters will be stored in the memory location called name.

name = input("Enter your name ")

Variable in Python

A variable is a named memory location, that stores a value, this value can change while the program is running.  In the example above:

• the name of the variable is name
• the value that is stored is whatever the name the user enters
• The the user can choose to change the value that is stored in name later in the program

We can print the value that is stored in a variable, by including the name of the variable in the print statement.  The following program prompts the user to enter their name, age and print them back to the screen.

name = input("What is your name: ")
age = input("What is your age: ")

print(name + " you are " + age + " years old !! ")

When variables are created in Python, we should also ensure that meaningful names are used so that one can remember what they represent. When creating variables, use words that describe the data that will be stored. Follow these rules when you create variables in Python:

• must begin with a letter of the alphabet or the underscore character
• cannot contain any space, therefore my name is not a valid variable name
• cannot be a reserved word (word with special meaning) in Python

Here are some examples of valid variable names in Python:

age
height
name 
length_of_room
_item
position23

Here is  a list of Python reserved words that you should avoid as variable names.

False               class               from                or
None                continue            global              pass
True                def                 if                  raise
and                 del                 import              return
as                  elif                in                  try
assert              else                is                  while
async               except              lambda              with
await               finally             nonlocal            yield
break               for                 not