자료구조 : 리스트

리스트 (list)

• 리스트 생성

  Ex.

  ```
  my_list = [1, 2, 3, 4]
  my_list = []
  my_list = list()
  my_list = list(range(5)) # [1, 2, 3, 4]
  ```

• 리스트 수정
  - access with index

  Ex.

  ```
  my_list[2] = -3 
  ```

• 리스트 추가
  - append(obj) : insert obj at the end of the list
  - insert(idx, obj) : insert obj before idx's index of the list

  Ex.

  ```
  my_list = [1, 2, 3, 4]
  my_list.append(100)  # my_list = [1, 2, 3, 4, 100]
  my_list.insert(3, 200) # my_list = [1, 2, 3, 200, 4, 100]
  my_list.insert(len(my_list, 500)) # my_list = [1, 2, 3, 200, 4, 100, 500]
  ```

• 리스트 삭제
  - del(list[idx]) : delete idx's element of the list
  - remove(obj) : delete the element whose value is obj of the list, if there are serval elements that have the same value of obj, delete the first one
  - pop() or pop(idx) : pop() ; delete the last element of the list, and return that value of the element.
  pop(idx) ; delete idx's element of the list, and return that value of the element

  Ex.

  ```
  my_list = [1, 2, 3, 4, 5]
  del my_list[2] # my_list = [1, 2, 4, 5]
  my_list.remove(4) # my_list = [1, 2, 5]
  my_list.pop() # my_list = [1, 2] and return 5
  my_list.pop(0) # my_list = [2] and return 1
  ```

• 리스트 정렬
  - sort(reverse = False) : sort the list in ascending order (default reverse = False)
  - sorted(list, reverse = False) : sort the list in ascending order (default reverse = False), and it returns the value(== sorted list)

  Ex.

  ```
  myL = [3, 2, 7, 1, 5]
  myL.sort() # myL = [1, 2, 3, 5, 7]
  myL.sort(reverse = True) # myL = [7, 5, 3, 2, 1]
  myL = sorted(myL) # myL = [1, 2, 3, 5, 7]
  myL = sorted(myL, reverse = True) # myL = [7, 5, 3, 2, 1]
  ```

• 리스트 연산 (덧셈 / 곱셈)

  Ex.

  ```
  a = [1, 2, 3, 4]
  b = [5, 6, 7, 8]
  c = a + b 		# 덧셈 : c = [1, 2, 3, 4, 5, 6, 7, 8]
  a = a * 2 		# 곱셈 : a = [1, 2, 3, 4, 1, 2, 3, 4]
  ``` 

• 리스트 함수 etc ... (extend, reverse, count, ...)
  - list1.extend(list2) : extend list1 to list1 + list2
  - reverse() : make the list reversed
  - count(obj) : return the number of elements whose value is obj in the list

  Ex.

  ```
  myL = [3, 2, 7, 1, 1, 1, 5]
  myL.reverse() # myL = [5, 1, 1, 1, 7, 2, 3]
  myL.count(1) # 3
  ############################################
  myL2 = [1, 2, 3]
  myL2.extend(myL) # myL2 = [1, 2, 3, 5, 1, 1, 1, 7, 2, 3]
  ```