First , We know Python 3 in , Yes 6 Standard data types , They are divided into variable and immutable .

Immutable data （3 individual ）：

• Number（ Numbers ）
• String（ character string ）
• Tuple（ Tuples ）

Variable data （3 individual ）：

• List（ list ）
• Dictionary（ Dictionaries ）
• Set（ aggregate ）

This is a Python 3 Medium 6 Standard data types , It includes their basic usage and common methods , It will be listed below , For future reference . First , We need to know about operators , Because these data types often use these operations and so on .

One 、 Operator

See ：Python Operator

Two 、 Standard data type

1. Number（ Numbers ）

• Python The number types of are int integer 、long Long integer 、float Floating point numbers 、complex The plural 、 And Boolean （0 and 1）.
• Python The number types of are int integer 、long Long integer 、float Floating point numbers 、complex The plural 、 And Boolean （0 and 1）.

2. String（ character string ）

• The string is Python The most commonly used data type in , We can use single quotes （’’） perhaps Double quotes （""） Create string .
• Strings are made up of numbers 、 Letter 、 A string of underscores 、 Is the type of data that represents text in a programming language .

2.1 Processing strings

# String form ： Use '' perhaps "" Create string 
str1 ='this is str1'
print(str1)

2.2 String commonly used methods

• 2.2.1 toggle case

   # 1.upper() Converts all lowercase letters in a string to uppercase 
  # character string .upper()
  s1 = "hello Python"
  print(s1.upper()) # HELLO PYTHON
  #2.lower() Converts all uppercase letters in a string to lowercase 
  # character string .lower()
  s2 = "HELLO PYTHON"
  print(s2.lower()) # hello python
  #3.swapcase() Swap the upper and lower case letters in the string 
  # character string .swapcase()
  s3 = "hello PYTHON"
  print(s3.swapcase()) # HELLO python
  #4.title() Title The letters in the string ( Capitalize the first letter of each word )
  # character string .title()
  s4 = "hello python hello world"
  print(s4.title()) # Hello Python Hello World
  #5.capitalize() Make the first letter in the string uppercase Capital function 
  # character string .captialize()
  s5 = "hello python hello world"
  print(s5.capitalize()) # Hello python hello world
  

• 2.2.2 Determine the content of the string

  # 1.isupper() Check whether the string is composed of uppercase letters 
  # Variable .isupper()
  # 2.islower() Check whether the string is composed of lowercase letters 
  # Variable .islower()
  # 3.istitle() Check whether the string meets the title requirements 
  # Variable .istitle()
  # 4.isalnum() Check whether the string is composed of numbers, letters and text 
  # Variable .isalnum()
  # 5.isalpha() Check whether the string is composed of letters and text 
  # Variable .isalpha()
  # 6.isdigit() Detect whether the string is 10 Hexadecimal characters （ Numbers ） *
  # True: Unicode Numbers ,byte Numbers （ Single byte ）, Full angle numbers （ Double byte ）
  # False: Chinese characters and numbers 
  # Error: nothing 
  # Variable .isdigit()
  # 7.isnumeric() Check whether the string is composed of numeric characters （ Numbers ）
  # True: Unicode Numbers , Full angle numbers （ Double byte ）, Chinese characters and numbers 
  # False: nothing 
  # Error: byte Numbers （ Single byte ）
  # Variable .isnumeric()
  # 8.isspace() Detect whether the string is composed of white space characters ( Invisible characters ) form *
  # Variable .isspace()
  

• 2.2.3 Judge what starts and ends

  # 1.startswith() Checks whether the string starts with the specified string *
  # Variable .startswith(' Detected string ')
  # 2.endswith() Checks whether the string ends with the specified string *
  # Variable .endswith(' Detected string ')
  

• 2.2.4 Text alignment

  # 1.center() Fills the string to the specified length with the specified characters , Center the original content 
  # Variable .center( Fill length )
  # Variable .center( Fill length , Fill character )
  # 2.ljust() Fills the string to the specified length with the specified characters , Align the original content to the left 
  # Variable .ljust( Fill length )
  # Variable .ljust( Fill length , Fill character )
  # 3.rjust() Fills the string to the specified length with the specified characters , Align the original content to the right 
  # Variable .rjust( Fill length )
  # Variable .rjust( Fill length , Fill character )
  # 4.zfill() zero fill Zero fill effect （ That is, the length is not enough 0 fill ）, Keep the content to the right 
  # Variable .zfill( The length of the entire string )
  

• 2.2.5 join() 、split() as well as partition()

  # 1.split() Cut a string with a specific string *
  # Variable .split( Cut characters )
  # Variable .split( Cut characters , Number of cuts )
  # 2.join() Concatenate container data into a string using a specific string *
  # Specific string .join( Containers )
  

• 2.2.6 Delete the blank string strip()

  # 1.strip() Remove the consecutive characters specified on the left and right sides of the string *
  # Variable .strip() By default, the left and right space characters are removed 
  # Variable .strip( Removed specified string )
  # 2.lstrip() Removes the consecutive characters specified to the left of the string 
  # Variable .lstrip() By default, the left and right space characters are removed 
  # Variable .lstrip( Removed specified string )
  # 3.rstrip() Removes the consecutive characters specified to the right of the string 
  # Variable .rstrip() By default, the left and right space characters are removed 
  # Variable .rstrip( Removed specified string )
  

• 2.2.7 String substitution replace()
• 2.2.8 String substitution makestran(),translate()
• 2.2.7 String formatting operation

3. Tuple（ Tuples ）

• Tuples are similar to lists , Tuple use （） Express . The inner elements are separated by commas , Tuples are immutable , You cannot assign values twice , Equivalent to read-only list .

  t = (100,'xiaoming','hello',1.23)
  print(t[0]) # 100
  t[3] = 666 # This is an illegal application 
  # TypeError: 'tuple' object does not support item assignment
  

4. List（ list ）

• List can complete the data structure implementation of most collection classes , Support for characters , Numbers , String, etc. . The list is Python The most common composite data type .

4.1 Common methods in the list

• 4.1.1 append() Method
  Modify the list object in place , Add a new element to the end of the list , Fast , Recommended

  list = [10,'a']
  list.append('b')
  print(list)
  # result : [10, 'a', 'b']
  

• 4.1.2 insert() Method
  Inserts the specified element into any specified position of the list object , This will move all elements behind the insertion position , It will affect the processing speed . When a large number of elements are involved , Avoid using . There are other functions like this movement ：remove(),pop(),del(), They also move the element after the operation position when deleting the last element .

  list = [10,'a']
  list.insert(1,'b')
  print(list)
  # result : [10, 'b', 'a']
  

Be careful : append() and insert() The method is the list method , Can only be called on a list , Cannot call... On other values , For example, strings and integers .

• 4.1.3 " + " Operator operation
  Copy the original list and the new list elements to the new list object in turn , Not really adding to the end , Instead, create a new list object . This approach involves a large number of replication operations , It is not recommended to operate on a large number of elements .

  list = [10,'a']
  list = list + ['b']
  print(list)
  # result : [10, 'a', 'b']
  

• 4.1.4 extend() Method
  Add all elements of the target list to the end of this list , It belongs to in-situ operation , Do not create new list objects .

  list = [10,'a']
  list.extend([20,'b'])
  print(list)
  # result : [10, 'a', 20, 'b']
  

Be careful : Additional append() and Expand extend() Differences in methods ：append() The method is to add the element decomposition of the data type to the list ;extend() Method to add the element as a whole .

• 4.1.5 Multiplication extension
  Use multiplication to expand the list , Generate a new list , The new list element is a multiple repetition of the original list element . Also suitable for multiplication expansion operations are , character string , Tuples .

  list = [10,'a']
  list2 = list * 3
  print(list2)
  # result : [10, 'a', 10, 'a', 10, 'a']
  

• 4.1.6 del The global method
  It can delete the element at the specified position in the list , You can also empty the list , Dictionaries can also be used del

  list = [10,'a','b']
  del list[1]
  print(list) # result : [10, 'b']
  del list
  print(list) # result : <class 'list'>
  

• 4.1.7 remove() Method
  Delete the first occurrence of the specified element , If the element does not exist, an exception is thrown

  list = [10,'a','b',30,'a']
  list.remove('a')
  print(list) # result : [10, 'b', 30, 'a']
  list.remove('c')
  print(list)
  # Throw an exception 
  # Traceback (most recent call last):
  # [10, 'b', 30, 'a']
  # File "C:Desktop/Test.py", line 10, in <module>
  # list.remove('c')
  # ValueError: list.remove(x): x not in list
  

If you know the subscript of the value to be deleted in the list ,del Statements are easy to use . If you know the value you want to delete from the list ,remove() It's easy to use .

• 4.1.8 pop() Method
  Deletes and returns the element at the specified index location , If no location is specified, the last element of the default action list ; If pop Parameter index bit exceeds , False report .

  list = [10,'a','b',30]
  print(list.pop(1)) # result : a
  print(list) # result : [10, 'b', 30]
  print(list.pop(6)) # result : IndexError: pop index out of range
  

• 4.1.9 sort() Sorting method
  sort() You can sort a list of values or a list of strings .

  # positive sequence 
  num = [2,5,-1,3.14,8,22,10]
  num.sort()
  print(num)
  # Output : [-1, 2, 3.14, 5, 8, 10, 22]
  print(sorted(num))
  # Output : [-1, 2, 3.14, 5, 8, 10, 22]
  # sort() and sorted() Method , The usage of the two is different 
  # The reverse 
  # Appoint reverse The key parameter is True
  num = [2,5,-1,3.14,8,22,10]
  num.sort(reverse=True)
  print(num)
  # Output : [22, 10, 8, 5, 3.14, 2, -1]
  print(sorted(num,reverse=True))
  # Output : [22, 10, 8, 5, 3.14, 2, -1]
  

  About sort() The method should pay attention to ：
  • sort() Method to sort the list on the spot .

    num = [2,5,-1,3.14,8,22,10]
    num = num.sort() # Wrong operation 
    print(num)
    

  • You can't sort a list that has both numbers and string values

    str1 = [1,3,5,7,'hello','world']
    str1.sort()
    print(str1)
    # TypeError: '<' not supported between instances of 'str' and 'int'
    

  • sort() Method to sort a string , Use "ASCII Character order ", Not the actual dictionary order . A lowercase letter a stay Capitalization z after .

    str1 = ['A','a','B','b','C','c']
    str1.sort()
    print(str1)
    # Output : ['A', 'B', 'C', 'a', 'b', 'c']
    # Sort in normal dictionary order 
    str2 = ['A', 'a', 'B', 'b', 'C', 'c']
    str2.sort(key=str.lower) # Treat all items in the list as lowercase 
    print(str2)
    

5. Dictionary（ Dictionaries ）

5.1 increase

• 5.1.1 Give the dictionary newly added " Key value pair "
  If “ key ” Already exists , Coverage “ Old key value pairs ”, If “ key ” non-existent , Then add “ Key value pair ”.

  info = {
  'name':'zz','age':18}
  info['age'] = 20 # Key already exists , Cover 
  info['job'] = 'student' # The key doesn't exist , newly added 
  print(info) # result : {'name': 'zz', 'age': 20, 'job': 'student'}
  

• 5.1.2 Python Dictionary update() Method
  Add all key value pairs in the new dictionary to the old dictionary object , If the key value pair has repetition, it will be overwritten directly

  info = {
  'name':'zz','age':18}
  info1 = {
  'name':'hh','sex':' male ','money':8000}
  info.update(info1)
  print(info)
  # result : {'name': 'hh', 'age': 18, 'sex': ' male ', 'money': 8000}
  

5.2 Delete

• 5.2.1 Python Dictionary clear() Method
  Delete all elements in the dictionary

  info = {
  'name':'zz','age':18,'sex':' male '}
  info.clear()
  print(info) # result : {}
  

• 5.2.2 Python Dictionary del The global method
  Can delete the element of the key specified in the dictionary , You can also delete the dictionary , The list can also be used del

  info = {
  'name':'zz','age':18,'sex':' male '}
  del info['name'] # Delete key is 'name' The key/value pair 
  print(info) # result : {'age': 18, 'sex': ' male '}
  del info # Empty dictionary 
  print(info)
  # Throw an exception ：
  # Traceback (most recent call last):
  # {'age': 18, 'sex': ' male '}
  # File "C:/Desktop/Test.py", line 26, in <module>
  # print(info)
  # NameError: name 'info' is not defined
  

  Here you can think about , Why clear() There is no exception when deleting the dictionary ？
  because ： use del The deleted dictionary no longer exists , While using clear() Is to clear all the elements in the dictionary . If you don't understand , I suggest you read it more , Experience deeply , You'll understand , At this time, I have to sigh that Chinese culture is broad and profound ！！！
• 5.2.3 Python Dictionary pop() Method
  Delete the value corresponding to the key specified in the dictionary , The return value is the deleted value

  info = {
  'name':'zz','age':18,'sex':' male '}
  print(info.pop('name')) # result : zz
  print(info) # result : {'age': 18, 'sex': ' male '}
  

• 5.2.4 Python Dictionary popitem() Method
  Randomly return and delete a pair of keys and values in the dictionary

  info = {
  'name':'zz','age':18,'sex':' male '}
  pop_info = info.popitem() # Randomly return and delete a key value pair 
  print(pop_info)
  # The output may be : ('sex', ' male ')
  

6. Set（ aggregate ）

Be careful ： aggregate （set） It's a Disordered non repetition Sequence of elements .

# 1. Create set 
info = set('hello')
print(info)
# Possible result : {'l', 'e', 'o', 'h'}

6.1 increase

Python There are two common ways to add collections , Namely add() and update().

• 6.1.1 Python aggregate add() Method
  Add the element to be passed in as a whole to the collection , The insertion position is random

  info = {
  'h', 'e', 'l', 'o'}
  info.add('python')
  print(info)
  # Possible result : {'h', 'e', 'python', 'l', 'o'}
  

• 6.1.2 Python aggregate update() Method
  Split the elements to be passed in , Pass as an individual into the collection

  info = {
  'h', 'e', 'l', 'o'}
  info.update('python')
  print(info)
  # Possible result : {'n', 'e', 't', 'o', 'h', 'y', 'p', 'l'}
  

6.2 Delete

• 6.2.1 Python aggregate remove() Method
  Delete elements from the collection , There is no throw exception

  info = {
  'h', 'e', 'python', 'l', 'o'}
  info.remove('python')
  print(info)
  # Possible result : {'e', 'l', 'h', 'o'}
  

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