Python Variables Guide

Variables

In computer programs, a variable is a location (address) in memory that holds a value. Variables in Python are entities that store values and can be manipulated. When a variable is assigned a value, it is created. It's important to note that in Python, a string can only be concatenated with another string. If you need to concatenate other types of data, you must first convert them into string format using the str() function.

Key Points:

Each variable has a name and stores a value.

Variables in Python do not have a fixed type; the type is determined dynamically based on the value assigned.

The str() function is used to convert non-string data into a string format for concatenation.

Variable Naming

When defining a variable, choose a name that clearly describes its purpose. Here are the rules for naming variables in Python:

The name must start with a letter or underscore and can include letters, numbers, and underscores thereafter.

Use meaningful names and avoid special characters like spaces, $, %, etc.

Variable names are case-sensitive.

Examples of poor naming:

variable1

my_var

info_1

Examples of good naming:

temperature

current_time

user_score

Constants

Constants are variables that store fixed, immutable values. Unlike variables, the values of constants never change during program execution. (Note: Python does not have a built-in constant mechanism.)

Key Point:

Constants are often used for readability and efficiency by storing fixed data in a single location.

Data Types

Data types determine the nature of data and how it is stored and manipulated. The main data types in Python are:

Integer (int): Represents whole numbers.

Float (float): Represents floating-point numbers.

Complex (complex): Represents complex numbers.

Additional Points:

Python automatically determines the type of variable when it is assigned a value.

The str() function is used to convert numbers to strings during output.

Input and Output

The following code demonstrates how to read and print input in Python:

a = input("Please enter an integer: ")print(a)

The input() function reads user input and returns a string.

The print() function outputs the string to the console.

Examples:

print("Hello, World!") outputs Hello, World!

a, b = "x", "y" assigns a = "x" and b = "y"

转载地址：http://bditz.baihongyu.com/

你可能感兴趣的文章