Different types of variables can perform different operations, so the type of the variable must be understood. Data types in python can be divided into:
Built-in types ：
Numeric type: Integer type int, floating point type float, complex number (complex) 3 5j
str:String
bool:Boolean value [True, False]
None: Null value, indicating that the variable has no determined value
list: List
tuple：tuple
dict：dict
set：Collection
Custom type:
##class: Class
Numeric type:
Integer type (int): There is only one type of int in python3, which can represent integers, for example: 10, -5, 10000
Floating point type (float): represents a real number with a decimal point, There are two representations:
Complex: represents an irrational number in mathematics , in the form: a bj
Boolean type (bool): represents the two states of the transaction, male and female, cloudy and sunny, light and dark Wait, it has only two values: True, False
None: represents an empty object, generally used for judgment, different from 0 and empty characters
String (str): In python, use quotes (single quotes, double quotes, triple quotes) to represent strings
Representation of string:
# Use single quotes to express: 'hello'# Use double quotes to express: "I use python"
# Use 3 A single quotation mark means: it can represent multi-line text, for example:
'''The great
's
motherland
'''
# It means 3 double quotation marks: it can represent multi-line text , for example:
"""Be optimistic about life and death,
Just do it if you don't accept it"""
Escape characters: Some special characters cannot Input from the keyboard can be represented by escape characters. In addition, whether it is a single quotation mark, double quotation mark or triple quotation mark string, the quotation mark is the string delimiter, and the quotation mark is not the content of the string. So how to enter a single quotation mark string? Indicates a single quote, which can also be expressed using escape characters. Common escape characters
| Escape characters | Description | Escape characters | Description | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| ##\' | represents an ordinary character single quote \n | line break |
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| \" | represents an ordinary character double quote \r | ##Enter | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
\\ |
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
\a | Ring | ##\t |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| \b | Delete one character back |
The computer cannot store it directly String, but we can encode the characters, for example, use 65 to represent uppercase character A, 66 to represent uppercase character B... etc. This representation method is the American ASCII code, which can only represent 127 characters, but for Americans That's enough. Once we can use integers to represent characters, we can easily represent integers in binary, and strings can be easily stored in the computer. 1.2 Type judgmentWe can use type and isinstance to test and judge the data type #type用法：
type(obj)
功能：返回obj的数据类型
参数：obj是你要测试变量或数值
示例：
age = 10
name = 'hello'
print(type(name),type(age))
#判断变量是否是指定类型
if type(age) is int:
print('是')
else:
print('否')
#isinstance用法：
isinstance(obj,typename)
功能：判断obj是否是指定类型，是返回True,否返回False
参数： objobj是你要判断的变量或数值
typename是指定数据类型,可以是int,float,str等。也可是一个
类型的元组,例如:(int,float)
示例：
age = 10
name = 'hello'
print(isinstance(age,int))
print(isinstance(name,(str,int)) #只要name是str或int的一种就返回True
if isinstance(age,int):
print('是')
else:
print('否')
#type和isinstance的区别
type判断基本类型是没问题的，但无法判断子类对象是父类的一种
isinstance可以判断子类对象是父类的一种
class A:
pass
class B(A):
pass
objA = A()
objB = B()
#输出否
if type(objB) is A:
print('是')
else:
print('否')
print(isinstance(objB,A)) #TrueCopy after login Conclusion:Use first isinstance 2. Operators and expressionsIn order to calculate the results in mathematics, we will write some formulas to calculate, for example:
This is a calculation formula in mathematics. There are similar formulas in python for calculation, called expressions. In the expression, 30 and 5 are called operands, called operators. The purpose of an expression is to compute a result. Expression composition:
Based on the above, the so-called expression is composed of operands and operators An expression that conforms to python syntax. To write expressions, you first need to learn operators. There are two things to know about operators
2.1 Arithmetic operatorsa = 20 b = 10 Copy after login
注意：
2.5 赋值运算符
注意：
a = 2 b = 3 a *= b + 2 #等价于 a = a * (b + 2) print(a) # a = 10 Copy after login 2.6 关系运算关系运算就是比较运算，如果表达式成立，返回True，否则返回False。关系运算的结果是布尔值。
注意：
2.7 逻辑运算逻辑运算符可以用于构造复杂条件。逻辑运算符包括：
在逻辑运算中，False、None、0、0.0、‘’（空字符串）被看做假（False），其它的看做真(True) 2.7.1 逻辑与
2.7.2 逻辑或
2.7.3 Logic Not
Summary: If a is true, the expression is False, otherwise the expression is True 2.8 Short-circuit calculation
2.9 Notes
|
The above is the detailed content of How to use python variable data types and operators. For more information, please follow other related articles on the PHP Chinese website!
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
