Python中有什么变量，我该如何宣布它们？

变量在Python中用于存储数据，它们像标签一样附着在值上，允许后续使用或修改这些值。命名变量需遵守规则：可包含字母、数字和下划线，但不能以数字开头；区分大小写；避免使用内置关键字；推荐使用snake_case风格。赋值时无需显式声明类型，直接使用=号赋值即可，例如name = "Alice"。可以一行赋多个值，如x, y, z = 1, 2, 3。Python会根据值自动确定变量类型，常见类型包括int、float、str、bool等。变量类型可变，但应谨慎处理以避免混淆。掌握变量的命名与赋值是构建表达式和程序的基础。

Variables in Python are like containers that hold data. You can think of them as labels you attach to values, so you can use or change those values later. Unlike some other languages, you don’t have to explicitly declare a variable before using it — just assign a value, and Python takes care of the rest.

Naming Variables Properly

Python has some basic rules for naming variables:

• They can contain letters, numbers, and underscores
• They can't start with a number
• They are case-sensitive (age and Age are different)
• Avoid using built-in keywords like if, for, while, etc.

Good examples:

user_age = 25
total_price = 99.99
is_valid = True

Bad examples:

1st_name = "John"     # Starts with a number
my-var = "test"       # Hyphens aren't allowed
class = "Math"        # 'class' is a keyword

A common style in Python is to use snake_case, where words are lowercase and separated by underscores.

Assigning Values to Variables

Declaring a variable in Python is simple: just pick a name and assign a value using the equals sign =.

name = "Alice"
count = 10
is_active = False

You can also do multiple assignments in one line:

x, y, z = 1, 2, 3

Or assign the same value to multiple variables:

a = b = c = 0

Python automatically determines the type of the variable based on the assigned value. So if you assign a string, it becomes a string; assign a number, and it's an integer or float depending on context.

Common Variable Types

Here are the most commonly used types you’ll see:

• int: whole numbers (e.g., 5, -3)
• float: decimal numbers (e.g., 3.14, -0.001)
• str: text (e.g., "hello", 'Python')
• bool: either True or False
• list, dict, tuple, etc., for more complex data

You can check a variable’s type using type():

print(type(name))   # <class 'str'>
print(type(count))  # <class 'int'>

One thing to remember: variables can change type after being set. For example:

x = 5      # x is int
x = "five" # now x is str

This flexibility is powerful but can also be confusing if not handled carefully.

基本上就这些。 Once you understand how variables work, you can start building expressions, functions, and programs around them. It’s not complicated, but getting the naming and assignment right early on will save you time later.

以上是Python中有什么变量，我该如何宣布它们？的详细内容。更多信息请关注PHP中文网其他相关文章！