Getting Started with Python (Part 5): Working with Variables

Working with Variables in Python

In this chapter, the theme is variables.

By using variables, you can reuse specific values in your program.

What Is a Variable?

A variable is a mechanism that allows you to give a name to a value so that you can reuse it later.

In Python, you can think of a variable as attaching a label to a value.

You can choose variable names freely, but there are some naming rules:

• A variable name cannot start with a number
• It can contain letters, numbers, and underscores
• Uppercase and lowercase letters are treated as different (msg and Msg are different)
• Python reserved words (words with special meanings in Python) cannot be used

To assign a value to a variable, use the = operator.

variable_name = value

Based on these rules, here is a sample program:

msg1 = "Hello"    # OK
msg2 = "Python"  # OK
2msg = "Python"  # NG (cannot start with a number)
if = "Python"    # NG (reserved word)
print(msg1)      # Hello
print(msg2)      # Python

Using Variables

If a variable holds a number, you can use it in calculations.

num1 = 100
num2 = 10
num3 = 1

print(num1 + num2)  # 110
print(num2 + num3)  # 11
print(num1 - num2)  # 90
print(num1 * num2)  # 1000
print(num1 / num2)  # 10.0 (division results in a floating-point number)

If a variable holds a string, you can concatenate it with other strings using +.

str1 = "Hop"
str2 = "Step"
str3 = "Jump"

print(str1 + str2 + str3)  # HopStepJump

If a variable holds a number, convert it to a string using the str() function before concatenating.

famicom = "The release year of the Famicom: "
birth = 1983

print(famicom + str(birth))
# The release year of the Famicom: 1983

Coming Up Next...

Thank you very much for reading!

The next chapter is titled “Working with Errors and Exceptions”.

Stay tuned!