Expression Variable

This document covers Python expressions and variables, including arithmetic operations, assignment, variable naming conventions, and practical examples for storing and manipulating values efficiently.

Introduction

Expressions in Python describe operations performed by the computer, such as arithmetic calculations. Variables are used to store and reuse values in code.

Python Expressions

Expressions are combinations of operands and operators that produce a result.

Arithmetic Operations

• Addition (+): Adds numbers. Example: 100 + 60 results in 160.
• Subtraction (-): Subtracts numbers. Example: 10 - 20 results in -10.
• Multiplication (*): Multiplies numbers. Example: 5 * 5 results in 25.
• Division (/): Divides numbers. Example: 25 / 5 results in 5.0; 25 / 6 results in approximately 4.167.
• Integer Division (//): Divides and rounds down to the nearest integer. Example: 25 // 6 results in 4.

Python follows mathematical conventions, performing multiplication before addition unless parentheses change the order.

1# Example of order of operations
2result = (32 + 32) * 60  # result is 1920

Variables in Python

Variables store values for later use. Assignment uses the equal sign (=).

1my_variable = 1  # Assigns 1 to my_variable
2my_variable = 10 # Updates my_variable to 10

The previous value is replaced by the new assignment.

Variables can store results of expressions:

1x = 10 + 20 + 30  # x is 60
2y = x / 22.5      # y is 2.666...
3x = y             # x is now 2.666...

Using meaningful variable names helps track code purpose and improves readability.

Variable Naming Conventions

• Use underscores (_) to separate words: total_min
• Use descriptive names: total_hour
• Variables can be updated, and dependent results will change automatically.

Example:

1total_min = 142
2# Convert minutes to hours
3total_hour = total_min / 60  # total_hour is approximately 2.367

Changing total_min updates total_hour without modifying other code.

Conclusion

Python expressions and variables enable efficient calculations and data management. Understanding operators, assignment, and naming conventions helps write clear, maintainable code.

FAQ