[learn Python from simple to deep] six data types

brief introduction

Python Some standard types are defined , Used to store various types of data .
Python There are currently six standard data types ：

• Numbers（ Numbers ）
• String（ character string ）
• List（ list ）
• Tuple（ Tuples ）
• Dictionary（ Dictionaries ）
• Set（ aggregate ）

Several classifications

Category one ：
These six data types can be subdivided into immutable data types and variable data types

Immutable data （3 individual ）：Number（ Numbers ）、String（ character string ）、Tuple（ Tuples ）
Variable data （3 individual ）：List（ list ）、Dictionary（ Dictionaries ）、Set（ aggregate ）

Category two ：
These six data types can be subdivided into 4 Number types and 5 Two sequence types , common 9 Number types .

4 The two types of numbers are ： integer (int), floating-point (float), The plural (complex), Boolean value (bool)
5 The two sequence types are ： character string (string), list (list), Tuples (tuple), Dictionaries (dict), aggregate (set)

【 notes 】 When we need to store a set of data , You need to use the sequence type , The sequence assigns an index to each element , The first is 0, The second is 1, Discuss and deduce in turn .

One 、 Numbers （Number）

Python3 Four different types of numbers are supported ：

int（ Long integer ）
float（ floating-point ）
complex（ The plural ）
bool（ Boolean type ）

【 Be careful 】 stay Python 3 in , There is only one integer type int, Expressed as a long integer , No, python2 Medium Long. stay Python2 There is no Boolean in , It uses numbers 0 Express False, use 1 Express True. To Python3 in , hold True and False Defined as a keyword , But their value is still 1 and 0, They can be added to numbers .

give an example ：

# Numerical type 
>>> n=100 # Define a variable 
#type: View data types of variables 
>>> print(type(n))

Output ：<class ‘int’>

>>> pi=3.14
>>>print(type(pi))

Output ：<class ‘float’>

Two 、 character string （String）

Data in double or single quotes , It's just a string .
The single character is in Python Is also used as a string .

# Character 
string1="Python"
print(type(string1))

Output ：<class ‘str’>

# Multiline string 
string3='''Python baidu '''
print(string3)
print(type(string3))

Output ：
Python
baidu

<class ‘str’>

3、 ... and 、 list （List）

Create a list , Just use different data items separated by commas square brackets [ ] Just round it up .
The data items of a list do not need to have the same type .

list1 = ["qing", "ping", 27]
list2 = [1, 2, 3, 4]
list3 = ["a", "b", "c"]

Four 、 Tuples （Tuple）

Tuples are similar to lists , But the element values of tuples cannot be modified or deleted , It can be sliced and connected .
Tuples are easy to create , Enclosed in parentheses , Separated by commas . Tuples use braces , The list uses brackets .

Tuple = () # Creating a tuple 
Tuple = ("a","b","c","d")
Tuple = ([1,2,3],"a",3,)

Be careful 1： Tuple of an element , Add a... At the back “,”

Tuple =(2022,)

Be careful 2： Arbitrary with “,” Separate sequences , Default is tuple .

>>> a = 1,2,3,4
>>> a
(1, 2, 3, 4)
>>> a =[1,2,3,4],5,"str"
>>> a
([1, 2, 3, 4], 5, 'str')

Be careful 3：Python Tuples tuple() Function to convert a list to a tuple .

5、 ... and 、 Dictionaries （Dictionary）

Dictionaries are stored in key value pairs , Elements can be key visit . Dictionaries are written by Curly braces { } Enclosed contains ,key : value Two parts .

 dict = {
'name':' Monitor of the class ', 'id':100, 'sex':'f', 'address':' Earth Asia China Beijing '}
print(dict["name"],dict["sex"])

6、 ... and 、 aggregate （Set）

A collection is an unordered and indexed collection . stay Python in , Sets are written in curly braces .
Be careful ： have access to Curly braces { } perhaps set() Function to create a collection , But to create an empty collection, you must use set() instead of { }, because { } Is used to create an empty dictionary ,

s1= {
"apple", "banana", "cherry"}
print(s1)