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Questions and Answers
Which of the following statements accurately describes a Python list?
Which of the following statements accurately describes a Python list?
- An immutable, unordered collection of unique items.
- A data type that can hold only numerical values.
- A fixed-size array used for storing strings.
- A mutable, ordered sequence of values. (correct)
Python lists can only contain elements of the same data type.
Python lists can only contain elements of the same data type.
False (B)
How do you access the element at index 3 in a list named my_list?
How do you access the element at index 3 in a list named my_list?
my_list[3]
Lists are defined using square ______.
Lists are defined using square ______.
What is the output of the following code?
my_list = [10, 20, 30, 40, 50]
print(my_list[-2])
What is the output of the following code?
my_list = [10, 20, 30, 40, 50]
print(my_list[-2])
Attempting to access an index that is out of range in a list will result in a syntax error.
Attempting to access an index that is out of range in a list will result in a syntax error.
Explain the concept of negative indexing in Python lists.
Explain the concept of negative indexing in Python lists.
In Python, the index -1 refers to the ______ element of a list.
In Python, the index -1 refers to the ______ element of a list.
Which of the following statements is true about Python lists?
Which of the following statements is true about Python lists?
Python lists do not allow duplicate values.
Python lists do not allow duplicate values.
Provide an example of creating a list containing an integer, a string, and a boolean value.
Provide an example of creating a list containing an integer, a string, and a boolean value.
A list that contains elements of different data types is known as a ______ list.
A list that contains elements of different data types is known as a ______ list.
Which of the following operations modifies a list in-place?
Which of the following operations modifies a list in-place?
List slicing creates a new list object, leaving the original list unchanged.
List slicing creates a new list object, leaving the original list unchanged.
Explain the difference between the append() and extend() methods for lists.
Explain the difference between the append() and extend() methods for lists.
The ______ method adds elements from another list to the end of the current list.
The ______ method adds elements from another list to the end of the current list.
What will be the output of the following code?
my_list = [1, 2, 3, 4, 5]
my_list.insert(2, 'hello')
print(my_list)
What will be the output of the following code?
my_list = [1, 2, 3, 4, 5]
my_list.insert(2, 'hello')
print(my_list)
The insert() method replaces the element at the specified index.
The insert() method replaces the element at the specified index.
How can you insert the value 'apple' at index 3 of a list named fruits without overwriting any existing element?
How can you insert the value 'apple' at index 3 of a list named fruits without overwriting any existing element?
The ______ method is used to insert an element at a specific index in a list.
The ______ method is used to insert an element at a specific index in a list.
Which method removes the first occurrence of a specified value from a list?
Which method removes the first occurrence of a specified value from a list?
The pop() method removes an item from a list based on its value, not its index.
The pop() method removes an item from a list based on its value, not its index.
How do you remove the element 'banana' from the list my_list = ['apple', 'banana', 'cherry']?
How do you remove the element 'banana' from the list my_list = ['apple', 'banana', 'cherry']?
To remove a specific item from a list by its value, you would use the ______ method.
To remove a specific item from a list by its value, you would use the ______ method.
If no index is specified, what does the pop() method do?
If no index is specified, what does the pop() method do?
Calling pop() on an empty list results in a ValueError.
Calling pop() on an empty list results in a ValueError.
How would you remove the last element from a list called data using the pop() method?
How would you remove the last element from a list called data using the pop() method?
Without specifying an index, the pop() method removes the ______ item from the list.
Without specifying an index, the pop() method removes the ______ item from the list.
What is the primary difference between using del my_list[index] and my_list.remove(value)?
What is the primary difference between using del my_list[index] and my_list.remove(value)?
The del keyword can only be used to remove elements from a list; it cannot remove the list itself.
The del keyword can only be used to remove elements from a list; it cannot remove the list itself.
Describe how the del keyword is used to remove the element at index 2 from a list named items.
Describe how the del keyword is used to remove the element at index 2 from a list named items.
The ______ keyword can be used to remove an item at a specific index or to delete the entire list.
The ______ keyword can be used to remove an item at a specific index or to delete the entire list.
What does the clear() method do to a list?
What does the clear() method do to a list?
The clear() method returns a new empty list rather than modifying the original list.
The clear() method returns a new empty list rather than modifying the original list.
What is the result of applying the clear() method to the list my_list = [1, 2, 3]?
What is the result of applying the clear() method to the list my_list = [1, 2, 3]?
The ______ method removes all elements from a list, resulting in an empty list.
The ______ method removes all elements from a list, resulting in an empty list.
Match each list method with its corresponding action:
Match each list method with its corresponding action:
Given the list numbers = [2, 3, 5, 2, 11, 2, 7], what will numbers.count(2) return?
Given the list numbers = [2, 3, 5, 2, 11, 2, 7], what will numbers.count(2) return?
The count() method can only be used with numerical lists.
The count() method can only be used with numerical lists.
Flashcards
What is a List in Python?
What is a List in Python?
An ordered, mutable set of values enclosed in square brackets
Can Lists Have Duplicate Values?
Can Lists Have Duplicate Values?
Yes, lists allow items with the same value because they are indexed.
What can be used as a List index?
What can be used as a List index?
An integer value or expression used to access elements.
What causes an IndexError?
What causes an IndexError?
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What happens with negative list indexes?
What happens with negative list indexes?
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What do negative indexes specify?
What do negative indexes specify?
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What does the range of indexes specify?
What does the range of indexes specify?
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What happens if you omit the start value of "Range of Indexes?"
What happens if you omit the start value of "Range of Indexes?"
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What happens if you omit the end value of "Range of Indexes?"
What happens if you omit the end value of "Range of Indexes?"
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What does the 'in' operator do?
What does the 'in' operator do?
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How to change the value of a list item?
How to change the value of a list item?
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How to change a range of item values?
How to change a range of item values?
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What does the extend() method do?
What does the extend() method do?
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What does the insert() method do?
What does the insert() method do?
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What does the remove() method do?
What does the remove() method do?
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What does pop() method do?
What does pop() method do?
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What does pop() do without an index?
What does pop() do without an index?
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What does the 'del' keyword do?
What does the 'del' keyword do?
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What does the clear() method do?
What does the clear() method do?
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What does a for loop do?
What does a for loop do?
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What does the sort() method do?
What does the sort() method do?
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How to sort in descending order?
How to sort in descending order?
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What does the count() method do?
What does the count() method do?
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Study Notes
Lists
- Lists are an ordered set of values enclosed in square brackets [].
- The values in a list can be modified, and lists are mutable.
- An index in square brackets [] can identify a specific value inside the list.
- Elements are the values that make up a list.
- Elements can be of any data type.
- Lists allow duplicate values because they are indexed.
- Example:
thislist = ["apple", "banana", "cherry", "apple", "cherry"]
Creating Lists
- Lists can be created with different data types like integers, strings, or mixed types.
myIntegerList = [1, 2, 3, 4, 5]creates a list of integers.myStringList = ["One", "Two", "Three"]creates a list of strings.myMixedList = [1, "Two", False, None]creates a list with mixed data types.myEmptyList1 = []andmyEmptyList2 = list()create empty lists.myList = list((1,2,3))creates a list from a tuple.
Working with List Index
- List indexing functions in the same way as string indexing.
- An integer value or expression can be used as an index.
- An
IndexErroroccurs if you try accessing an element that does not exist in the list. - A negative index counts the elements from the end of the list.
- Forward indexing refers to elements starting from the beginning of the list.
- For example, in a list
[45, 56, 67, 20], the forward indexes are 0, 1, 2, and 3.
- For example, in a list
- Backward indexing refers to elements starting from the end of the list.
- For example, in a list
[45, 56, 67, 20], the backward indexes are -4, -3, -2, and -1.
- For example, in a list
- Lists are ordered and mutable, allowing modification of elements.
- Example:
myIntegerList = [1, 2, 3, 4, 5]myIntegerList[3] = 10changes the element at index 3 from 4 to 10.- Output:
[1, 2, 3, 10, 5]
Traversing a List
- Negative indexing starts from the end of the list.
- Example:
thislist = ["apple", "banana", "cherry"],print(thislist[-1])outputs"cherry".
- Example:
- A range of indexes specifies where to start and end the range.
- When specifying a range, a new list is returned with the specified items.
- Example:
thislist = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]print(thislist[2:5])outputs['cherry', 'orange', 'kiwi'].
- The search starts at index 2 (included) and ends at index 5 (not included).
- The first item’s index is zero.
- Example:
- The range starts from the first item if the start value is left out.
- Example:
thislist = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]print(thislist[:4])outputs['apple', 'banana', 'cherry', 'orange'].
- Example:
- The range continues to the end of the list if the end value is omitted.
- Example:
thislist = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]print(thislist[2:])outputs['cherry', 'orange', 'kiwi', 'melon', 'mango'].
- Example:
- Negative indexes specify to start the search from the end of the list.
- Example:
thislist = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]print(thislist[-4:-1])outputs['orange', 'kiwi', 'melon'].
- Example:
- The
inoperator checks if a value exists in a list.- Example:
myIntegerList=[1,2,3,4,5]checker = 3 in myIntegerListprint(checker)outputsTrue.
- Example:
Altering Items in a List
- A specific item’s value can be changed by referring to its index number.
- Example:
thislist = ["apple", "banana", "cherry"]thislist[1] = "blackcurrant"changes the second item from"banana"to"blackcurrant".- Output:
['apple', 'blackcurrant', 'cherry']
- Example:
- A range of item values can be changed by defining a list with the new values and referring to the range of index numbers you want to insert the new values into.
- Example:
thislist = ["apple", "banana", "cherry", "orange", "kiwi", "mango"]thislist[1:3] = ["blackcurrant", "watermelon"]changes the second and third items.- Output:
['apple', 'blackcurrant', 'watermelon', 'orange', 'kiwi', 'mango']
- Example:
Inserting Items in a List
- The
extend()method appends elements from another list to the current list.- Example:
thislist = ["apple", "banana", "cherry"]tropical = ["mango", "pineapple", "papaya"]thislist.extend(tropical)- Output:
['apple', 'banana', 'cherry', 'mango', 'pineapple', 'papaya']
- The elements are added to the end of the list.
- Example:
- The
insert()method inserts a new list item without replacing any existing values. The specified index indicates where the item should be inserted.- Example:
thislist = ["apple", "banana", "cherry"]thislist.insert(2, "watermelon")- Output:
['apple', 'banana', 'watermelon', 'cherry']
- Example:
Removing Items in a List
- The
remove()method removes the specified item.- Example:
thislist = ["apple", "banana", "cherry"]thislist.remove("banana")- Output:
['apple', 'cherry']
- Example:
- The
pop()method removes the item at the specified index.- Example:
thislist = ["apple", "banana", "cherry"]thislist.pop(1)- Output:
['apple', 'cherry']
- Example:
- The
pop()method removes the last item if the index is not specified.- Example:
thislist = ["apple", "banana", "cherry"]thislist.pop()- Output:
['apple', 'banana']
- Example:
- The
delkeyword removes the specified index or the entire list completely.- Example:
thislist = ["apple", "banana", "cherry"]del thislist[0]will remove the first element (apple).- Output:
['banana', 'cherry']
- Example:
- The
clear()method empties the list.- Example:
thislist = ["apple", "banana", "cherry"]thislist.clear()- Output:
[]
- Example:
Iterating Items in a List
- A
forloop can loop through list items.- Example:
thislist = ["apple", "banana", "cherry"]for x in thislist: print(x)will output each item on a new line.
- Example:
- The
range()andlen()functions loop through list items by referring to their index number to create a suitable iterable.- Example:
thislist = ["apple", "banana", "cherry"]for i in range(len(thislist)): print(thislist[i])will output each item on a new line.
- Example:
- A
whileloop can loop through list items. You must use thelen()function to determine the length of the list and increment the index by 1 after each iteration.- Example:
thislist = ["apple", "banana", "cherry"]i=0while i < len(thislist): print(thislist[i]); i=i+1
- Example:
- Example:
fruits = ["apple", "banana", "cherry", "kiwi", "mango"]newlist = []for x in fruits: if "a" in x: newlist.append(x)print(newlist)outputs['apple', 'banana', 'mango'].
Sorting Items in a List
- The
sort()method sorts the list items in ascending order.- Example:
thislist = [100, 50, 65, 82, 23]thislist.sort()- Output:
[23, 50, 65, 82, 100]
- Example:
- To sort descending, use
reverse = True.- Example:
thislist = ["orange", "mango", "kiwi", "pineapple", "banana"]thislist.sort(reverse = True)- Output:
['pineapple', 'orange', 'mango', 'kiwi', 'banana']
- Example:
- The default
sort()method is case sensitive, which means it will sort all capital letters before lower case letters.- Example:
thislist = ["banana", "Orange", "Kiwi", "cherry"]thislist.sort()- Output:
['Kiwi', 'Orange', 'banana', 'cherry']
- Example:
- To perform a case-insensitive sort, use the
str.lowerfunction as the key.- Example:
thislist = ["banana", "Orange", "Kiwi", "cherry"]thislist.sort(key = str.lower)- Output:
['banana', 'cherry', 'Kiwi', 'Orange']
- Example:
Count Method
- The
count()method returns the number of times the specified element appears in the list.- Example:
numbers = [2, 3, 5, 2, 11, 2, 7]count = numbers.count(2)- Output: Count of 2: 3
- Example:
List Methods
append(): Adds an element at the end of the list.clear(): Removes all the elements from the list.copy(): Returns a copy of the list.count(): Returns the number of elements with the specified value.extend(): Adds the elements of a list (or any iterable) to the end of the current list.index(): Returns the index of the first element with the specified value.insert(): Adds an element at the specified position.pop(): Removes the element at the specified position.remove(): Removes the item with the specified value.reverse(): Reverses the order of the list.sort(): Sorts the list.
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