Briefly describe how to define a variable type in Python?

This article mainly talks about how to define a Python variable. The concept of variable is basically the same as the equation variable in junior high school algebra, but in the computer program, Variables can not only be numbers, but also any data type.

Variables are represented by a variable name in the program. The variable name must be a combination of uppercase and lowercase English, numbers, and _, and cannot start with a number, such as:

a = 1

Variablea is an integer.

t_007 = 'T007'

The variable t_007 is a string.

Answer = True

VariableAnswer is a Boolean value True.

In Python, the equal sign = is an assignment statement. Any data type can be assigned to a variable. The same variable can be assigned repeatedly, and it can be a variable of different types, for example:

# -*- coding: utf-8 -*-
a = 123 # a是整数
print(a)
a = 'ABC' # a变为字符串
print(a)

This kind of language whose variable type is not fixed is called dynamic language , corresponding to static language. In static languages, the variable type must be specified when defining a variable. If the type does not match when assigning a value, an error will be reported. For example, Java is a static language, and the assignment statement is as follows (// represents a comment):

int a = 123; // a是整数类型变量
a = "ABC"; // 错误：不能把字符串赋给整型变量

Compared with static languages, dynamic languages ​​are more flexible, for this reason.

Please do not equate the equal sign of the assignment statement with the mathematical equal sign. For example, the following code:

x = 10
x = x + 2

If you understand it mathematically x = x 2, it is not true anyway. In the program, the assignment statement first calculates the expression on the right x 2, get the result 12, and assign it to the variable x. Since the previous value of x was 10, after reassignment, the value of x becomes 12.

Finally, it is also important to understand how variables are represented in computer memory. When we write:

a = 'ABC'

, the Python interpreter does two things:

1. Creates a string of 'ABC' in memory;

2 .Create a variable named a in memory and point it to 'ABC'.

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