Worksheet 5.43 Group Work: Functions with Lists and Loops



A list holds items in order and you can get the value at an index, just like you can with strings. You can also use negative indices, just like you can with strings. You can use the slice operator [start:end] with lists to get a new list by copying part of a list, just like you can with strings. The new list will include the item at the start index (inclusive) and all elements up to the end index - 1.

def list_get(lst):
    print(lst[0])
    print(lst[:2])
    return lst[-2]
l = ["hi", 3, 'buy', 4]
print(list_get(l))

There are several built-in functions in Python that work on lists such as max, min, len, and sum.

Lists are objects of the list class and have methods that operate on list objects using dot notation (name.method()) such as append, pop, and extend.

def list_trans(lst):
    lst.append(3)
    lst.pop(2)
    return lst
l1 = [2, 5, 7]
print(list_trans(l1))

You can also reverse a list or sort it.

def list_trans(lst):
    r = lst.reverse()
    print(lst)
    print(r)

l1 = [2, 5, 7]
list_trans(l1)

A for-each loop in Python will loop though the items in a list starting with the item at index 0, then index 1, and so on till the last item in the list.

How do you loop just a set number of times? You can use the built-in range function to do this.

def total_at_odd_indices(alist):
---
def total_at_odd_indices(alist)  #paired
---
     total = 0
---
     for i in range(1,len(alist),2):
---
     for i in range(1,len(alist)):  #paired
---
         total += alist[i]
---
         total += i  #paired
---
     return total

A while loop repeats while a Boolean expression is True.

If you worked in a group, you can copy the answers from this page to the other group members. Select the group members below and click the button to share the answers.