Python 3 | Lists

Lists | Coding_Challenges_1.py

"""
Create a function called every_three_nums that has one parameter named start.

The function should return a list of every third number between start and 100 (inclusive). 
For example, every_three_nums(91) should return the list [91, 94, 97, 100]. 
If start is greater than 100, the function should return an empty list.

"""

#Write your function here
def every_three_nums(start):
  return list(range(start, 101, 3))


print(every_three_nums(91))
# print: [91, 94, 97, 100]

Lists | Coding_Challenges_10.py

"""

Create a function named double_index that has two parameters, a list named lst and a single number as index.

The function should return a new list where all elements are the same as in lst except for the element at index, which should be double the value of the element at index of lst.

If index is not a valid index, the function should return the original list.

For example, the following code should return [1,2,6,4] because the element at index 2 has been doubled:

double_index([1, 2, 3, 4], 2)
After writing your function, un-comment the call to the function that we’ve provided for you to test your results.

"""

#Write your function here
def double_index(lst, index):
  if index >= len(lst):
    return lst
  else:
    new_lst = lst[0:index]
    new_lst.append(lst[index]*2)
    new_lst = new_lst + lst[index+1:]
    return new_lst


print(double_index([3, 8, -10, 12], 2))
# print: [3, 8, -20, 12]

Lists | Coding_Challenges_2.py

"""

Create a function called append_size that has one parameter named lst.

The function should append the size of lst (inclusive) to the end of lst. The function should then return this new list.

For example, if lst was [23, 42, 108], the function should return [23, 42, 108, 3] because the size of lst was originally 3.

"""

#Write your function here
def append_size(lst): 
  lst.append(len(lst))
  return lst


print(append_size([23, 42, 108]))
# print: [23, 42, 108, 3]

Lists | Coding_Challenges_3.py

"""

Write a function named combine_sort that has two parameters named lst1 and lst2.

The function should combine these two lists into one new list and sort the result. Return the new sorted list.

"""

#Write your function here
def combine_sort(lst1, lst2):
  unsorted = lst1 + lst2
  sorted_list = sorted(unsorted)
  return sorted_list


print(combine_sort([4, 10, 2, 5], [-10, 2, 5, 10]))
# print: [-10, 2, 2, 4, 5, 5, 10, 10]

Lists | Coding_Challenges_4.py

"""

Write a function named larger_list that has two parameters named lst1 and lst2.

The function should return the last element of the list that contains more elements. 

If both lists are the same size, then return the last element of lst1.

"""

#Write your function heredef 
def larger_list(lst1, lst2): 
  if len(lst1) >= len(lst2):
    return lst1[-1]
  elif len(lst2) > len(lst1): 
    return lst2[-1]
  else:
    return lst1[-1]


print(larger_list([4, 10, 2, 5], [-10, 2, 5, 10]))
# print: 5

Lists | Coding_Challenges_5.py

"""

Write a function named append_sum that has one parameter named lst.

The function should add the last two elements of lst together and append the result to lst. It should do this process three times and then return lst.

For example, if lst started as [1, 1, 2], the final result should be [1, 1, 2, 3, 5, 8].

"""

#Write your function here
def append_sum(lst):
  lst.append(lst[-1] + lst[-2])
  lst.append(lst[-1] + lst[-2])
  lst.append(lst[-1] + lst[-2])
  return lst


print(append_sum([1, 1, 2]))
# print: [1, 1, 2, 3, 5, 8]

Lists | Coding_Challenges_6.py

"""

Create a function called middle_element that has one parameter named lst.

If there are an odd number of elements in lst, the function should return the middle element.
If there are an even number of elements, the function should return the average of the middle two elements.

"""

#Write your function here
def middle_element(lst): 
  if len(lst) % 2 == 0:
    sum = lst[int(len(lst)/2)] + lst[int(len(lst)/2) - 1]
    return sum / 2
  else:
    return lst[int(len(lst)/2)]



print(middle_element([5, 2, -10, -4, 4, 5]))
# print: -7.0

Lists | Coding_Challenges_7.py

"""

Create a function named more_frequent_item that has three parameters named lst, item1, and item2.

Return either item1 or item2 depending on which item appears more often in lst.

If the two items appear the same number of times, return item1.

"""

#Write your function here
def more_frequent_item(lst, item1, item2): 
  if lst.count(item1) >= lst.count(item2):
    return item1
  else:
    return item2

  
print(more_frequent_item([2, 3, 3, 2, 3, 2, 3, 2, 3], 2, 3))
# print: 3

Lists | Coding_Challenges_8.py

"""

Create a function named more_than_n that has three parameters named lst, item, and n.

The function should return True if item appears in the list more than n times. The function should return False otherwise.

"""

#Write your function here
def more_than_n(lst, item, n):
  if lst.count(item) > n:
    return True
  else:
    return False


print(more_than_n([2, 4, 6, 2, 3, 2, 1, 2], 2, 3))
# print: True

Lists | Coding_Challenges_9.py

"""

Create a function named remove_middle which has three parameters named lst, start, and end.

The function should return a list where all elements in lst with an index between start and end (inclusive) have been removed.

For example, the following code should return [4, 23, 42] because elements at indices 1, 2, and 3 have been removed:

remove_middle([4, 8 , 15, 16, 23, 42], 1, 3)

"""
#Write your function here
def remove_middle(lst, start, end):
  return lst[:start] + lst[end+1:]


print(remove_middle([4, 8, 15, 16, 23, 42], 1, 3))
# print: [4, 23, 42]