* operator and range() in python 3.x has many uses. One of them is to initialize the list.
Code : Initializing 1D-list list in Python
# Python code to initialize 1D-list # Initialize using star operator # list of size 5 will be initialized. # star is used outside the list. list1 = [0]*5 # Initialize using list comprehension # list of size 5 will be initialized. # range() is used inside list. list2 = [0 for i in range(5)] print("list1 : ", list1) print("list2 : ", list2) |
Output:
list1 : [0, 0, 0, 0, 0] list2 : [0, 0, 0, 0, 0]
Here, Only difference is star operator is used outside of the list. And range() is used inside. These two can also be used with a list within the list or Multidimensional list.
Code : list within list using * operation and range()
# Python code to # initialize list within the list # Initialize using star operator list1 = [[0]]*5 # Initialize using range() list2 = [[0] for i in range(5)] # list of 5 "[0] list" is initialized. # Both list are same so far print("list1 : ", list1) print("list2 : ", list2) |
Output:
list1 : [[0], [0], [0], [0], [0]] list2 : [[0], [0], [0], [0], [0]]
The real glitch is with the multidimensional list. While dealing with a multidimensional list, initialization method matters a lot. Both methods * operator and list comprehension behaves differently.
Code : Multi-dimensional List
# Consider same previous example. # Initialize using star operator. star_list = [[0]]*5 # Initialize using list Comprehension. range_list = [[0] for i in range(5)] star_list[0] = 8 # Expected output will come. range_list[0] = 8 # Expected output. ''' Output: star_list = [8, [0], [0], [0], [0]] range_list = [8, [0], [0], [0], [0]] ''' # Unexpected output will come. star_list[2].append(8) ''' Since star_list[2] = [0]. so it will find for all [0] in list and append '8' to each occurrence of [0]. And will not affect "non [0]" items is list.''' range_list[2].append(8) # expected output. print("Star list : ", star_list) print("Range list : ", range_list) |
Output:
Star list : [8, [0, 8], [0, 8], [0, 8], [0, 8]] Range list : [8, [0], [0, 8], [0], [0]]
If someone wants to deal with 1D-array, one can use anything. But with the multidimensional array, one should use list comprehension.
