1. Chapter 5: Lists and Dictionaries
C10061 – Introduction to Computer Programming
Kent State University
Chapter 5: Lists and Dictionaries

2. Chapter Topics Covered
Lists vs. tuples
List mutability
List creation, lengths and operators
List indexing and slicing
New features of lists
List methods
Chapter 5: Lists and Dictionaries

3. Lists Lists are another type of sequence.
Similar to tuples and do everything tuples do
Mutable (changeable)
Use functions to find lengths
Use operators to determine conditions
Use indexing
Use slicing
Use methods for manipulation
Chapter 5: Lists and Dictionaries

4. Lists Creating a list is the same as creating a
tuple, only the elements are enclosed in [ ].
Example: empty_list = []
Example: string_list = [“value1”, “value2”]
number_list = [2.5,50]
combo_list = [7,”string”]
Chapter 5: Lists and Dictionaries

5. Lists Use len(list_name) to find how many elements exist in the list.
Use the in operator to check for conditions.
Use indexing for sequential or random access.
Use slicing with beginning and ending points.
Chapter 5: Lists and Dictionaries

6. Lists: New Features Assigning a new value to an element
Note: Not applicable for creating new elements
in the list (will generate an IndexError).
Example: current_list = [“One”,Two”,“Three”]
current_list[1] = “Zero”
Result: ['One', 'Zero', 'Three']
Chapter 5: Lists and Dictionaries

7. Lists: New Features Assigning a new value to a slice
Note: Single list replaces a two-element slice.
The number of elements decreases by 1.
Example: current_list = [“One”,“Two”,“Three”,”Four”]
current_list[1:3] = “Zero”
Result: ['One', 'Zero', 'Three']
Chapter 5: Lists and Dictionaries

8. Lists: New Features Deleting a list element using the del command
Note: The gap created by a deletion is filled
automatically; all elements shift left one position.
Example: current_list = [“One”,“Two”,“Three”,”Four”]
del current_list[0]
Result: [‘Two', ‘Three', ‘Four']
Chapter 5: Lists and Dictionaries

9. Lists: New Features Deleting a slice using the del command
Note: The gap created by a deletion is filled
automatically; all elements shift left one position.
Example: current_list = [“One”,“Two”,“Three”,”Four”]
del current_list[:3]
Result: ['Four']
Chapter 5: Lists and Dictionaries

10. Lists: append( ) Function
Add a new element to the end of the list
Example: current_list = [“One”,“Two”,“Three”,”Four”]
new_element = “Five”
current_list.append(new_element)
Result: ['One', 'Two', 'Three', 'Four', 'Five']
Chapter 5: Lists and Dictionaries

11. Lists: remove( ) Function
Remove the first occurrence of a value
Example: current_list = [“One”,“Two”,“Two”,”Four”]
remove_element = “Two”
if remove_element in current_list:
current_list.remove(remove_element)
Result: ['One', 'Two', 'Four']
Chapter 5: Lists and Dictionaries

12. Lists: sort( ) Function
Sorts the elements of the list in
ascending order
Example: current_list = [“One”,“Two”,“Three”,”Four”]
current_list.sort( )
Result: ['Four', 'One', 'Three', 'Two']
Chapter 5: Lists and Dictionaries

13. Lists: reverse( ) Function
Sorts the elements of the list in
descending order
Example: current_list = [“One”,“Two”,“Three”,”Four”]
current_list.reverse( )
Result: ['Four', 'Three', 'Two', 'One']
Chapter 5: Lists and Dictionaries

14. Lists: count( ) Function
Returns the number of occurrences of a
specific value
Example: current_list = [“One”,“Two”,“Two”,”Four”]
search = “Two”
number = current_list.count(search)
print number
Result: 2
Chapter 5: Lists and Dictionaries

15. Lists: index( ) Function
Returns the first position number of
where a specific value occurs
Example: current_list = [“One”,“Two”,“Two”,”Four”]
search = “Two”
number = current_list.index(search)
print number
Result: 1
Chapter 5: Lists and Dictionaries

16. Lists: insert( ) Function
Inserts a specific value at a specific
position
Example: current_list = [“One”,“Two”,“Two”,”Four”]
new = “Three”
current_list.insert(2,new)
Result: ['One', 'Two', 'Three', 'Two', 'Four']
Chapter 5: Lists and Dictionaries

17. Lists: pop([i]) Function
Returns a value at a specific position (i)
and removes the value from the list
Example: current_list = [“One”,“Two”,“Two”,”Four”]
new = current_list.pop(1)
print new
print current_list
Result: Two
['One', 'Two', 'Four']
Chapter 5: Lists and Dictionaries

18. Lists: pop( ) Function from the list
Returns and removes the last element
from the list
Example: current_list = [“One”,“Two”,“Two”,”Four”]
last = current_list.pop( )
print last
print current_list
Result: Four
['One', 'Two', ‘Two']
Chapter 5: Lists and Dictionaries