Skip to main content

Section 9.4 List operations

The + operator concatenates lists:
Similarly, the * operator repeats a list a given number of times:
The first example repeats four times. The second example repeats the list three times.

Activity 9.4.1.

What is printed by the following statements? 
alist = [4, 2, 8, 6, 5]
alist = alist + 999
print(alist)
  • [4, 2, 8, 6, 5, 999]
  • You cannot concatenate a list with an integer.
  • Error, you cannot concatenate a list with an integer.
  • Yes, in order to perform concatenation you would need to write alist+[999]. You must have two lists.
  • [[4, 2, 8, 6, 5], 999]
  • You cannot concatenate a list with an integer. This would cause an error, not create a new list.
  • [4, 2, 8, 6, 5]
  • This will cause an error, but alist will remain unchanged.

Activity 9.4.2.

What is printed by the following statements? 
alist = [1, 3, 5]
blist = [2, 4, 6]
print(alist + blist)
  • 6
  • Concatenation does not add the lengths of the lists.
  • [1, 2, 3, 4, 5, 6]
  • Concatenation does not reorder the items.
  • [1, 3, 5, 2, 4, 6]
  • Yes, a new list with all the items of the first list followed by all those from the second.
  • [3, 7, 11]
  • Concatenation does not add the individual items.

Activity 9.4.3.

What is printed by the following statements? 
alist = [1, 3, 5]
print(alist * 3)
  • 9
  • Repetition does not multiply the lengths of the lists. It repeats the items.
  • [1, 1, 1, 3, 3, 3, 5, 5, 5]
  • Repetition does not repeat each item individually.
  • [1, 3, 5, 1, 3, 5, 1, 3, 5]
  • Yes, the items of the list are repeated 3 times, one after another.
  • [3, 9, 15]
  • Repetition does not multiply the individual items.
You have attempted of activities on this page.
PrevTopNext