Variables and assignment

A variable is a name that refers to a value. The = sign assigns the value on its right to the name on its left. Create a new file named variables.py in your python-roadmap folder and run it as you did in Chapter 1.

name = "Sam"
sessions = 3
print(name)
print(sessions)

Sam
3

Update a value

Assigning a new value to the same name replaces its previous value. Python reads the statements in order.

sessions = 3
sessions = 4
print(sessions)

4

Choose clear names

Variable names can contain letters, digits, and underscores, but cannot start with a digit. Names are case-sensitive: study_minutes and Study_minutes are different. Use descriptive lowercase names with underscores, such as minutes_per_session. Avoid spaces and Python keywords such as class.

Why this works

The name on the left of = receives the value calculated on the right. Reassignment changes what that name refers to from that point onward; earlier output does not change retroactively. A descriptive name helps a reader understand what a number measures.

Practice

Create variables for your name, the number of study sessions you plan, and the minutes in each session. Print each value. Then change the number of sessions, save, and rerun the script.

Try another case

After count = 2 and then count = count + 3, what does print(count) show?