Naming Variables

1.6. Naming Variables#

It is important you give your variables appropriate names - like how you might label boxes at home. If you don’t choose descriptive variable names, it can be very difficult for yourself or others to read your code. This will become increasingly important as you write longer and more complex programs.

Below are two examples of code that calculates the cost of 4 pens and 2 highlighters. Which is easier to interpret?

Program 1

a = 2.89
b = 1.97
c = 4 * a + 2 * b
print(c)

Program 2

pen = 2.89
highlighter = 1.97
cost = 4 * pen + 2 * highlighter
print(cost)

In addition to using descriptive names, there are rules that you must follow when choosing a variable name. A variable name:

Must start with a letter or an underscore character
Can only contain alpha-numeric characters and underscores

Further, variable names are case sensitive. This means that age and Age, are not the same.

age = 32
Age = 17

print(age)
print(Age)

Finally, you must ensure you don’t name your variables using keywords. Keywords are special words in Python that have a special meaning. You will notice that often they will be formatted in a different colour. For example, print is a keyword. If you end up assigning a value to a keyword, you will overwrite it and your code won’t work properly.

print = "hello"
print(print)