Python Unit 3: Data Structures and Lists

Questions and Answers

What is the index of the first element in a Python list?

0 (correct)

-1

None of the above

What does the negative index -2 represent in a list?

The second item from the end (correct)

The last item of the list

The first item of the list

The second item from the beginning

Which of the following will correctly return the items from the third to the fifth position in the list?

thislist[2:5] (correct)

thislist[2:4]

thislist[3:5]

thislist[:5]

Which of the following statements about Python lists is true?

A list can contain multiple identical items. Signup and view all the answers

What will be the output of print(thislist[-4:-1]) for thislist = ['apple', 'banana', 'cherry', 'orange', 'kiwi', 'melon', 'mango']?

['orange', 'kiwi', 'melon'] Signup and view all the answers

How can you access the third item in the list named thislist?

thislist[2] Signup and view all the answers

Which expression correctly checks if 'banana' is in the list?

'banana' in thislist Signup and view all the answers

Which built-in Python function is NOT applicable to sequences?

append() Signup and view all the answers

What is a key difference between Python lists and arrays in C/C++/Java?

Python lists can contain elements of multiple types. Signup and view all the answers

What will be printed by print(thislist[:4]) if thislist = ['apple', 'banana', 'cherry', 'orange', 'kiwi']?

['apple', 'banana', 'cherry', 'orange'] Signup and view all the answers

Which operation is NOT supported by Python sequences?

Choosing random items Signup and view all the answers

If list1 = ['Rohan', 'Physics', 21, 69.75], what does list1[0] return?

Rohan Signup and view all the answers

What is the effect of leaving out the end value in slicing, like thislist[2:]?

It will start from index 2 and include all items until the end. Signup and view all the answers

What does the following code snippet print? list1 = ['a', 'b', 'c']; print(list1[1])

'b' Signup and view all the answers

What will happen if you attempt to access an index that is out of range in a Python list?

It will raise an IndexError. Signup and view all the answers

For a list that contains integers, what does the expression thislist[-3] return if thislist = [1, 2, 3, 4, 5]?

3 Signup and view all the answers

What does list1[1:3] return if list1 = ['a', 'b', 'c', 'd']?

['b', 'c'] Signup and view all the answers

Which method would you use to remove a specific element from a list?

remove() Signup and view all the answers

What will be the output of this code: `list = [1, 2, 3]; list.pop(); print(list)`?

[1, 2] Signup and view all the answers

How can you determine the number of elements in a list?

len(list) Signup and view all the answers

What is the result of the code `list = [1, 2, 5, 6]; max(list)`?

6 Signup and view all the answers

What will be the output of `l1 = [1, 2, 3]; l2 = [4, 5]; print(l1 + l2)`?

[1, 2, 3, 4, 5] Signup and view all the answers

To iterate through the elements of a list, which construct is used?

for Signup and view all the answers

What will the following code print? `list = [1, 2, 3]; list[0] = 'New'; print(list)`

[New, 2, 3] Signup and view all the answers

Which of the following statements is true about Python lists?

Lists can contain different data types. Signup and view all the answers

What will be the output of the following code: print(list1[1:]) if list1 = ['a', 'b', 'c', 'd']?

['b', 'c', 'd'] Signup and view all the answers

What does the negative index -1 represent in a Python list?

The last element of the list Signup and view all the answers

Which method would you use to add an element at a specific position in a Python list?

insert() Signup and view all the answers

What will the following code print: list = ['Student', 'Teacher', 'Parent']; print(list[2:5])?

['Parent'] Signup and view all the answers

What is the correct output when using the sort() method on the list ['Student', 'Teacher', 'Parent', 'Friend']?

['Friend', 'Parent', 'Student', 'Teacher'] Signup and view all the answers

If you want to combine a list with another iterable in Python, which method should you use?

extend() Signup and view all the answers

When accessing elements with a range in Python list slicing, which statement is correct?

The start index is inclusive and the end index is exclusive. Signup and view all the answers

Which code snippet accurately demonstrates using negative indexing in Python?

list[-2] Signup and view all the answers

What will the output be for the code: list = ['Python', 'Java', 'C++']; list.insert(1, 'JavaScript'); print(list)?

['Python', 'JavaScript', 'Java', 'C++'] Signup and view all the answers

If you want to update the first element of a list named 'list' that holds elements ['a', 'b', 'c'], which of the following is correct?

list[0] = 'x' Signup and view all the answers

What does the `pop()` method return when called on a list?

The element removed from the specified index Signup and view all the answers

Which of the following operations allows you to create a new tuple from two existing tuples?

Using the <code>+</code> operator Signup and view all the answers

What will be the output of `my_list.count(3)` if `my_list = [1, 2, 3, 4, 3]`?

2 Signup and view all the answers

What will happen if you try to access an index that does not exist in a tuple?

An IndexError will be raised Signup and view all the answers

Which method would you use to sort the elements of a list in ascending order?

sort() Signup and view all the answers

Which statement correctly describes tuples in Python?

They can hold a mixture of data types Signup and view all the answers

How do you explicitly delete a tuple in Python?

del tup Signup and view all the answers

What does `my_list.index(3)` return if `my_list = [1, 2, 3, 4, 3]`?

2 Signup and view all the answers

What is the output of `print(my_list)` after executing `my_list.reverse()` if `my_list = [1, 2, 3, 4]`?

[4, 3, 2, 1] Signup and view all the answers

What is the key difference between a list and a tuple in Python?

Lists are mutable while tuples are immutable Signup and view all the answers

What type of data can be used as keys in a Python dictionary?

Immutable data types such as strings, numbers, or tuples Signup and view all the answers

What will happen if you try to use a list as a key in a dictionary?

A TypeError will be raised Signup and view all the answers

Which of the following is a valid way to define a Python dictionary?

my_dict = {1: 'One', 2: 'Two', 3: 'Three'} Signup and view all the answers

How are key-value pairs in a dictionary formatted?

Key-value pairs separated by a colon and wrapped in curly braces Signup and view all the answers

What will be the output of the following code? `d1 = {'a': 1, 'b': 2, 'a': 3}; print(d1)`

{'a': 3, 'b': 2} Signup and view all the answers

Which of the following statements is true regarding dictionary values?

Values can be of any data type and can repeat Signup and view all the answers

What is the correct syntax for creating an empty dictionary in Python?

empty_dict = {} Signup and view all the answers

In Python dictionaries, how do you access values associated with keys?

Utilizing square brackets along with the key Signup and view all the answers

What function would you use to find the number of elements in a list?

len() Signup and view all the answers

Which method would you use to add an element to the end of a list?

append() Signup and view all the answers

How can a tuple with a single element be correctly defined?

single_tuple = ('Tuple',) Signup and view all the answers

What will occur if you attempt to access an index in a tuple that exceeds its length?

It will raise an IndexError. Signup and view all the answers

How can you access the last element of a list named my_list?

my_list[-1] Signup and view all the answers

What is the output of trying to access tuple_[1.0] from tuple_ = ('Python', 'Tuple', 'Ordered', 'Collection')?

tuple indices must be integers or slices, not float Signup and view all the answers

What will the result of the operation my_list.remove(4) be if my_list = [1, 2, 3, 4, 4]?

[1, 2, 3, 4] Signup and view all the answers

How does negative indexing work in Python tuples?

Negative indices allow access to elements from the end of the tuple. Signup and view all the answers

What does the pop() method return if called without an index on a list named my_list?

The last element Signup and view all the answers

Which code line correctly prints elements between the 1st and 3rd indices of a tuple?

print(tuple_[1:3]) Signup and view all the answers

Which function is used to get the highest value in a list?

max() Signup and view all the answers

What will be displayed as a result of the following operation: my_list = [1, 2, 3]; my_list.extend([4, 5])?

[1, 2, 3, 4, 5] Signup and view all the answers

What will be printed by the code print(tuple_[:-4]) if tuple_ = ('Python', 'Tuple', 'Ordered', 'Immutable', 'Collection', 'Objects')?

('Python', 'Tuple', 'Ordered') Signup and view all the answers

Which method is used to reverse the order of elements in a list?

reverse() Signup and view all the answers

What will happen if you attempt to create a tuple without parentheses but include a trailing comma, such as single_tuple = 'Tuple',?

This will create a tuple with a single string element. Signup and view all the answers

Which of the following statements is true regarding tuple slicing?

Slicing can return elements based on indices and is used frequently. Signup and view all the answers

What output will the following code produce? my_list = [1, 2, 3]; my_list.insert(1, 'a')

[1, 'a', 2, 3] Signup and view all the answers

What will my_list look like after executing the code my_list = [1, 2, 3]; del my_list[0]?

[2, 3] Signup and view all the answers

What type of error will be raised if a non-integer is used as an index in a tuple?

TypeError Signup and view all the answers

What indexing error is shown when trying to access more elements than are present in a tuple?

tuple index out of range Signup and view all the answers

What happens when you attempt to change an immutable tuple directly?

It raises a 'tuple object does not support item assignment' error. Signup and view all the answers

Which operator would you use to combine two tuples into a single tuple?

The + operator Signup and view all the answers

What does the * operator do when applied to a tuple?

It repeats the elements of the tuple a specified number of times. Signup and view all the answers

Which function can be used to get the number of elements in a tuple?

len() Signup and view all the answers

Can mutable objects be changed when they are contained within a tuple?

Yes, you can change mutable objects such as lists within a tuple. Signup and view all the answers

What will be the output of the expression (2, 5) * 3?

(2, 5, 2, 5, 2, 5) Signup and view all the answers

Which statement correctly describes how tuples handle accidental modifications?

Tuples are safer than lists as they prevent accidental modifications. Signup and view all the answers

Which function can be used to determine the maximum value in a tuple?

max() Signup and view all the answers

What is true about the cmp() function when comparing two tuples?

It returns 0 if the tuples are equal. Signup and view all the answers

Why can tuples be used as dictionary keys while lists cannot?

Lists can change their contents. Signup and view all the answers

What is the result of the expression (1, 2, 3) + (4, 5, 6)?

(1, 2, 3, 4, 5, 6) Signup and view all the answers

What does the expression ('Hi!',) * 4 return?

('Hi!', 'Hi!', 'Hi!', 'Hi!') Signup and view all the answers

What will be the result when attempting to access a key that does not exist in a Python dictionary?

It raises a KeyError. Signup and view all the answers

What will the result of 3 in (1, 2, 3) evaluate to?

True Signup and view all the answers

Which method would correctly add a new key-value pair to an existing dictionary?

dict['School'] = 'DPS School' Signup and view all the answers

What will be the output of L[1:] if L = ('spam', 'Spam', 'SPAM!')?

('Spam', 'SPAM!') Signup and view all the answers

What will happen if you try to delete a key that does not exist in a Python dictionary?

It raises a KeyError. Signup and view all the answers

Which function is used to find the minimum value in a tuple?

min(tuple) Signup and view all the answers

What types can be used as keys in a Python dictionary?

Strings, numbers, or tuples. Signup and view all the answers

What is a key characteristic of tuples compared to lists?

Tuples are ordered and immutable. Signup and view all the answers

After executing the following code, what will be the output? dict = {'Name': 'Zara', 'Age': 7, 'Name': 'Manni'}. What is dict['Name']?

'Manni' Signup and view all the answers

What will be the output of the line print(type(tuple_)) if tuple_ = 4, 5.7, 'Tuples', ['Python', 'Tuples']?

<class 'tuple'> Signup and view all the answers

What does the built-in function len(tuple) return?

The length of the tuple. Signup and view all the answers

What does the 'clear()' method do when called on a dictionary?

It removes all entries from the dictionary. Signup and view all the answers

What will the code produce when executing 'del dict' on a defined dictionary?

Deletes the entire dictionary. Signup and view all the answers

What represents a nested tuple?

All of the above Signup and view all the answers

What will happen if a comma is omitted from a single-item tuple like (5)?

It will create an integer. Signup and view all the answers

Which of the following statements about dictionary keys is true?

Keys must be unique and immutable. Signup and view all the answers

If a dictionary is initialized as dict = {['Name']: 'Zara', 'Age': 7}, what will happen?

It raises a TypeError due to an unhashable type. Signup and view all the answers

What will be printed after executing these commands: dict = {'Name': 'Zara', 'Age': 7}; del dict['Name']; print(dict)?

{'Age': 7} Signup and view all the answers

What happens when you use the keyword del on a tuple variable?

It raises an error stating that item deletion is not supported. Signup and view all the answers

Which operation can be performed on tuples?

Repeating the entire tuple. Signup and view all the answers

What does the count() method return when applied to a tuple?

The number of occurrences of a specified element. Signup and view all the answers

Which of the following statements about the index() method in tuples is true?

It can accept a start index to search from. Signup and view all the answers

How can you check for the existence of an element in a tuple?

Using the not in operator. Signup and view all the answers

Given the output of count() method, what does the output 'Count of 2 in T1 is: 5' indicate?

The integer 2 appears five times in the first tuple. Signup and view all the answers

What is the tuple after the operation tuple_ = tuple_ * 3 when tuple_ originally is ('Python', 'Tuples')?

('Python', 'Tuples', 'Python', 'Tuples', 'Python', 'Tuples') Signup and view all the answers

What will be printed if you check membership using 'print('Tuple' in tuple_)' where tuple_ is ('Python', 'Tuple', 'Ordered')?

True Signup and view all the answers

What output is expected from the print statement: print('Items' in tuple_) when tuple_ is defined as ('Python', 'Tuple', 'Ordered')?

The string 'Items' is absent. Signup and view all the answers

What will the output be when trying to access tuple_ after executing del tuple_ if tuple_ was initially ('Python', 'Tuple')?

NameError: name 'tuple_' is not defined. Signup and view all the answers

What will be the output of the command `print(Employee['Name'])` if `Employee` is defined as `Employee = {'Name': 'Dev', 'Age': 20, 'salary': 45000, 'Company': 'WIPRO'}`?

Dev Signup and view all the answers

Which statement correctly describes how to update an existing value in a dictionary?

Assign a new value to the existing key using <code>Dict[key] = value</code>. Signup and view all the answers

What is the result of executing d3 = d1 | d2 in Python?

{'a': 2, 'b': 4, 'c': 30, 'a1': 20, 'b1': 40, 'c1': 60} Signup and view all the answers

What will happen if you attempt to access a key that does not exist in a dictionary using indexing?

It will raise a KeyError. Signup and view all the answers

What does the method dict.copy() return?

A shallow copy of the dictionary Signup and view all the answers

What is the output of `print(Dict)` after executing the code `Dict = dict([(4, 'Rinku'), (2, 'Singh')])`?

Both A and B are correct. Signup and view all the answers

What will the output be of executing d1.clear()?

An empty dictionary Signup and view all the answers

How are dictionary keys defined in Python?

Keys must be unique and immutable. Signup and view all the answers

What will be printed after executing `print(Dict)` if `Dict` is initialized as `Dict = {}` and then three items are added?

{0: 'Peter', 2: 'Joseph', 3: 'Ricky'} Signup and view all the answers

Which statement about dictionary keys in Python is true?

Keys must be unique within a dictionary Signup and view all the answers

What method can be used to safely access a value in a dictionary without raising an error for a nonexistent key?

get() Signup and view all the answers

What will be the output of print(d1.get('x', 10)) if 'x' is not a key in d1?

10 Signup and view all the answers

What will be the output of the command `print(Dict['Emp_ages'])` if `Dict` contains the key 'Emp_ages' with the value (20, 33, 24)?

(20, 33, 24) Signup and view all the answers

Which method can be used to create a new dictionary from an existing one with only specific keys?

dict.fromkeys() Signup and view all the answers

Which of the following operations is NOT permitted on dictionary keys?

Using a list as a key. Signup and view all the answers

What is the output of executing dict1.update(dict2) if dict1 = {'a': 1} and dict2 = {'a': 2, 'b': 3}?

{'a': 2, 'b': 3} Signup and view all the answers

What will the expression len(d1) return if d1 = {'a': 1, 'b': 2, 'c': 3}?

3 Signup and view all the answers

Which of the following correctly describes a Python dictionary?

It stores data as key-value pairs. Signup and view all the answers

What type of values can a dictionary hold in Python?

Any Python object Signup and view all the answers

Study Notes

Data Structures in Python: Lists and Tuples

Lists Introduction

The basic data structure in Python is the sequence, where each element is assigned an index starting from 0.
Python includes six built-in sequence types; the most common are lists and tuples.
Operations applicable to all sequence types: indexing, slicing, adding, multiplying, and membership checking.
Python has functions to determine sequence length, largest, and smallest elements.

Python Lists

A list is a sequence of comma-separated items defined in square brackets, e.g., list1 = ["Rohan", "Physics", 21, 69.75].
Lists can contain mixed data types and are ordered, mutable collections.
Lists are similar to arrays in C/C++/Java but can hold different data types in Python.
Items can be accessed, modified, added, or removed, and duplicates are allowed.

Accessing Lists

List items can be accessed using their index with zero-based numbering.
Negative indexing allows access from the end, e.g., -1 for the last item.
Slicing can return a range of items, e.g., thislist[2:5] gives the third to fifth items.
The in keyword checks for item presence in the list.

List Operations

Lists support comprehensive operations:
- Accessing Elements: Using indices for direct access, e.g., list[0] for the first item.
- Adding Elements: Use append (adds to end) and insert (adds at specific index).
- Sorting: sort() method sorts lists either in ascending or descending order.
- Updating Elements: Modify items directly by their index.
- Removing Elements: remove() deletes by item value; pop() removes last or specified item.
- Length: len() provides the count of elements in the list.
- Maximum/Minimum: max() and min() return largest and smallest items, respectively.
- Concatenation: Use the + operator to join lists together.
- Iteration: Loop through items using a for-loop.

Working with Lists

Lists are mutable and can be manipulated by adding, removing, or modifying items.
Creation uses square brackets; access items through their indices or slices.
Methods like clear() (removes all elements) and copy() (creates a copy) enhance list functionality.

Tuple Introduction

Tuples are similar to lists but are defined in parentheses, e.g., tup1 = ("Rohan", "Physics", 21, 69.75).
They can also include mixed data types and are indexed starting from 0.
Unlike lists, tuples are immutable: their content cannot be modified or removed.
An empty tuple is instantiated with (); a single-value tuple requires a trailing comma, e.g., (50,);.

Accessing Values in Tuples

Access values in tuples using indices or slicing similar to lists, e.g., tup[1].
Create new tuples via concatenation of existing tuples as tuples cannot be modified in place.

Tuple Operations

Tuples support concatenation using the + operator and repetition using the * operator.
Membership testing with "in" and "not in" is applicable to tuples as well.

These notes summarize the principles of handling lists and tuples in Python, their accessibility, mutability comparisons, and available operations and methods.### Python Tuples

A tuple is an immutable, ordered collection of elements, created by enclosing elements in parentheses and separating them with commas.
Example of tuple creation: tuple1 = (1, 2, 3).
Tuples can contain diverse data types, including other tuples, lists, strings, or dictionaries.
Single-element tuples must have a comma, e.g., single_tuple = (1,).