Containers for Data: Variables

In programming, a variable is like a container that holds data.

Just as we store important files on a USB drive or in the cloud, we use variables in programming to store and retrieve values when needed.

A variable is a reserved space in the computer’s memory where data is stored for later use. By assigning a value to a variable, we can access and manipulate the data efficiently.

Note: The space in the computer where a variable’s value is stored is called memory. A variable serves as a reference to the stored value.

In programming, declaring a variable is like preparing a container to hold data.

By declaring a variable, we assign a name to this container, allowing us to retrieve its stored value using that name whenever needed.

For example, the Python code below declares a variable named age but does not assign it a value yet.

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age = None

age is the name of the variable, and in Python, None means "nothing is put inside yet."

In Python, you do not need to follow complex syntax; simply defining the name of the variable is enough.

Assigning a value to a variable is like putting an item in the prepared container.

When assigning a value to a variable, we use the = symbol.

Unlike in general mathematics, in programming, = means assigning the value on the right to the variable on the left.

For example, the code below assigns the value 10 on the right to the variable age on the left.

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age = 10

The variable age now holds the number 10.

This value can be used to represent that some entity is 10 years old.

With the declared variable age, we can retrieve this number anytime using its name.

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new_age = age + 5  # 10 + 5 = 15

print(new_age)         # Prints 15

In the code above, the variable new_age holds the value 15, which is 5 added to the value stored in the age variable.

Also, we can use print(age) to display the value stored in the age variable on the screen.

Note: In Python, the = symbol is called the assignment operator. To compare if two values are the same, use ==.

Just as the item inside a container can be replaced, the value held by a variable can also be changed at any time.

For example, if you assign 10 to age and then reassign 20 to it, age will hold 20.

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age = 10  # Assign 10 to age
age = 20  # Reassign 20 to age

print(age)  # Prints 20

The 10 that was previously stored is no longer held by the age variable.

In this way, a variable allows you to store a specific value and change it whenever needed, aiding in flexible data handling in a program.