Introduction to Python programming-from getting started to practicing-note 2_ list

Source: Internet
Author: User
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List Introduction Basics
    • Use square brackets [] to represent the list, separated by commas
    • Print (list name) prints the internal contents of the list, including the square brackets and the quotation marks of the strings
    • Access the elements in the list, tell the location/index of the element to list name [index]
    • Number of indexes starting from 0
    • Print (list name [index]) prints a single element, excluding square brackets and string quotes
    • Access the last element of a list
      • List name [-1] to access the last element of the list
      • List name [-2] the second-to-last element of the access list ... And so on
    • list name [] Create an empty list
    • When using escape characters such as '/n ', be sure to use them in quotation marks. Suppose the message is a variable
      • Print ('/nmessage ') will prompt for errors
      • Print ('/n ' +message) is correct, wraps first, then prints message variable contents

Modify, add, and delete elements in a list
  • modifying list elements
    • How to replace: List name [index]= ' new element '
    • Change is permanent, unrecoverable.
  • Add a new element to the list
    • Method Append () example: Names.append (' Zoe ') adds the element ' Zoe ' to the end of the list names
    • Method Insert () Example: Names.insert (0, ' Zoe ') inserts the element ' Zoe ' before the element with the index 0 in the list names, and then moves the subsequent element to the right one position
  • Remove an element from the list
    • Statement del
      • Example: Del names[0] Delete the element on index 0 in the list names
      • Note that Del is a statement, not a method
      • Del Delete element, you need to know the index of the element to delete first
    • Method Pop ()
      • Deletes the last element of the list and returns the delete value
      • Example: Poped_n=names.pop () deletes the last element of the list names and saves the number in Poped_n
    • Method Remove ()
      • Delete an element by value
      • You don't need to know where the element you want to delete is located
      • Example: Names.remove (' Zoe ') delete list names in Zoe

Organization List
  • Method Sort
    • Sort by element in alphabetical order : Names.sort () Sorts the elements in the list names alphabetically by the first letter
    • The sort is permanent .
    • Reverse sort, pass-through parameter Reverse=true example: Names.sort (reverse=true) sorts the elements in the list names by the first letter, in reverse order
  • function sorted
    • Example: print (sorted (names)) prints the elements in the list names in alphabetical order, sorted by the first letter. But do not change the original sort of names
    • Sort of is temporary
    • Reverse sort, passing parameters reverse=true Example: Print (sort (names,reverse=true)) prints the elements in the list names in the first letter, sorted alphabetically, in reverse order
  • Method Reverse ()
    • Example of an arrangement of inverted list elements: Names.reverse () Reverses the order of the elements in the list names, not the alphabetical order
    • permanent , want to restore the original order, and then reverse once again
  • function len ()
    • Calculates the list length, which is the number of elements in the list
    • The number of calculated list elements is starting from 1, and several are
    • Example: Len (names) calculates the number of elements in the list names, and returns 5 if there are 5 elements.
  • using (-1) The method of accessing the last element will cause an error only if the list is empty, otherwise this method is in any case a proper way.
  • An error message is returned when an element that does not exist in the access list, or an index that is accessed exceeds the list

Introduction to Python programming-from getting started to practicing-note 2_ list

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