In the previous article, we learned how to run Python programs.

Now it’s time to understand how Python stores data.

Consider this line of code:

name = "Anna"

Most programming languages would describe name as a variable.

Python programmers use that term too.

However, there’s a more precise way to think about it:

name is a name.

What Does = Actually Do?

This statement:

name = "Anna"

means:

Create the name name and bind it to the value "Anna".

After that, we can use the name anywhere in our program.

print(name)

The output is:

Anna

A Name Can Be Used Many Times

For example:

name = "Anna"

print(name)
print(name)
print(name)

The result is:

Anna
Anna
Anna

Each time, Python looks up the value currently associated with the name name.

A Name Can Be Rebound

Later, we can write:

name = "John"

Now:

print(name)

prints:

John

The name now refers to a different value.

Naming Rules

A name may contain letters, digits, and underscores.

For example:

user
user_name
age
counter2

There are a few simple rules.

A name cannot begin with a digit.

This is invalid:

2users = 10

Names also cannot contain spaces.

This is incorrect:

user name = "Anna"

Instead, write:

user_name = "Anna"

Choosing Good Names

A good name should describe what it represents.

For example:

age = 18

is much more informative than:

x = 18

Code that’s easy to read is usually easier to understand and maintain.

For example:

user_name = "Anna"
print(user_name)

Even someone seeing the project for the first time can immediately understand what the code is doing.

Reserved Words

Some words already have special meaning in Python.

For example:

if
for
while
class

These are keywords, and they can’t be used as names.

For example:

for = 10

results in a syntax error.

What We Learned Today

Today we introduced one of the most fundamental concepts in Python.

  • A name allows us to refer to data.
  • The = operator binds a name to a value.
  • The same name can be used many times.
  • Later, a name can be rebound to a different value.
  • Good names make code easier to read.
  • Python keywords cannot be used as names.

Try It Yourself

Create a new Python file and experiment with it.

name = "Anna"
age = 20

print(name)
print(age)

name = "John"

print(name)

Try changing the values and the names.

For example, replace "Anna" with your own name, or add another variable called city.

What’s Next?

Now we know how to associate names with values.

But what kinds of values can Python store?

Why does this work:

age = 18

just as well as this?

name = "Anna"

In the next article, we’ll meet Python’s two most fundamental data types:

numbers and strings.