How to define variables in Python?

In Python, variables can be understood as containers for storing data. When we need to use or manipulate data, we can define variables to store the data so that we can easily call and process the data. The following will introduce how to define variables in Python.

1. Naming rules

In Python, the naming rules for variables are very flexible and usually need to follow the following rules:

1. Variable names consist of letters, underscores and numbers The first digit cannot be a number.
2. Variable names can use uppercase and lowercase letters, but Python is case-sensitive.
3. Variable names must not use reserved words, such as if, else, etc.
4. Variable names should be descriptive and can clearly describe the meaning of the stored data.

According to these rules, we can derive some legal Python variable names:

a, b, c # Single letter or letter combination
hello, world # String
my_num, index, max_value #Descriptive variable name

2. Assignment method

In Python, there are two ways to assign values ​​to variables: using the equal sign (=) and using functions (For example, input() function, range() function, etc.).

1. Using the equal sign

The first way to use a variable is to use the equal sign to assign a value to the variable. For example:

age = 18
name = "Lucy"
height = 1.65

In this example, we define three variables: age, name, and height. They store the integer 18, the string "Lucky" and the floating point number 1.65 respectively.

It should be noted that when we use the equal sign to assign a value to a variable, Python will automatically determine the variable type based on the assigned value. For example, in the above example, age is automatically defined as an integer type, name is automatically defined as a string type, and height is automatically defined as a floating point type.

2. Using functions

Another way to assign values ​​is to use functions. For example:

name = input("Please enter your name:")
numbers = range(10)

In this example, we use the input() function and range () function and assigns its results to the name and numbers variables.

It should be noted that when we use a function to assign a value to a variable, Python will assign the return value of the function to the variable. For example, the input() function returns the string entered by the user, and the range() function returns an integer sequence from 0 to 9.

3. Variable types

In Python, variables have many different types, including integers, floating point numbers, Boolean values, strings, lists, tuples, and dictionaries. When defining variables, we need to choose the appropriate type to store the required data. For example:

age = 18 # Integer type
height = 1.65 # Floating point type
is_student = True # Boolean type
name = "Lucy" # String type
scores = [80, 90, 85, 95] # List type
info = {"name": "Lucy", "age": 18} # Dictionary type

It should be noted that variables in Python Types can be changed dynamically at runtime. For example:

age = 18 # Integer type
print(type(age)) # Output integer type
age = "18" # String type
print(type(age)) #Output string type

In this example, we first define age as an integer type, and then reassign it to the string type. Finally, you can see that the type of age has changed through the type() function.

4. Variable calculations and operations

In Python, the calculations and operations of variables are similar to most other programming languages, such as addition, subtraction, multiplication, division, comparison, logical operations, etc. The following will introduce some common operations:

1. Addition, subtraction, multiplication and division of variables

The addition, subtraction, multiplication and division operations in Python are the same as those in other programming languages, for example:

a = 3 5 # Addition
b = 7 - 2 # Subtraction
c = 2 * 5 # Multiplication
d = 10 / 3 # Division
e = 10 // 3 # Integer division
f = 10 % 3 # Remainder

2. Comparison operations of variables

Comparison operations in Python include equal to, not equal to, greater than, and less than , greater than or equal to and less than or equal to operations, for example:

a = 10
b = 20
print(a == b) # False
print(a != b) # True
print(a > b) # False
print(a < b) # True
print(a >= b) # False
print(a <= b) # True

3. Logical operations on variables

Logical operations in Python include and, or, and not operations, for example:

a = True
b = False
print(a and b) # False
print(a or b) # True
print(not a) # False

Summary

The above is in Python An introduction to methods of defining variables, naming rules, assignment methods, variable types and common operations. When writing Python programs, defining variables is a basic knowledge that must be mastered, which can better help developers manage and manipulate data.

The above is the detailed content of How to define variables in Python?. For more information, please follow other related articles on the PHP Chinese website!