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
