ExamAdept

Which of the following statements about Python variables is true?

A:

Python is a statically typed language.

B:

A variable must be declared with a type before it can be used.

C:

Python allows multiple assignments in a single line.

D:

A variable's scope is determined by the type of data it holds.

Answer: C

Python is a dynamically typed language. In Python, a variable's type is inferred from the value it's assigned. A variable's scope is determined by where it's defined in the code.

For example:

a, b, c = 1, 2, 3

This statement assigns the values 1, 2, and 3 to the variables a, b, and c, respectively.

You can also assign the same value to multiple variables in one line:

a = b = c = "Orange"

This statement assigns the value "Orange" to the variables a, b, and c.

If you have a collection of values in a list, tuple, etc. Python allows you to extract the values into variables. This is called unpacking. For example:

fruits = ["apple", "banana", "cherry"]
a, b, c = fruits

This statement extracts the values "apple", "banana", and "cherry" from the list fruits and assigns them to the variables a, b, and c, respectively.

📖

What is the output of the following code:

my_string = "hello"
my_string[1] = "a"
print(my_string)

A:

hello

B:

hallo

C:

An error is raised

D:

None of the above

Answer: C

In Python, strings are immutable, which means their individual characters cannot be modified once they're created.

Attempting to change a character of a string using the index operator [ ] results in a TypeError.

📖

What is the output of the following code:

my_list = [1, 2, 3]
my_list[1] = 4
print(my_list)

A:

[1, 2, 3]

B:

[1, 4, 3]

C:

[4, 2, 3]

D:

An error is raised

Answer: B

In this code, the variable my_list is initially assigned a list containing the values 1, 2, and 3.

The second element of the list (which has an index of 1) is then changed to 4 using the assignment operator =.

When my_list is printed to the console, it shows the modified list [1, 4, 3].

📖

Which of the following is a valid way to check if a value is in a list called my_list?

A:

if my_value in my_list

B:

if my_list[ my_value ]

C:

if my_value in my_list == True

D:

All of the above

Answer: A

In Python, the in and not in operators can be used to check if a value is or is not in a list, respectively.

📖

What is the value of y after executing the following code:

x = [1, 2, 3]
y = x
x = [4, 5, 6]
print(y)

A:

[4, 5, 6]

B:

[1, 2, 3]

C:

[1, 2, 3, 4, 5, 6]

D:

An error is raised

Answer: B

In this code, the variable x is initially assigned a list containing the values 1, 2, and 3.

The variable y is then assigned the same list that x holds a reference to.

However, when x is reassigned a new list containing the values 4, 5, and 6, y still holds a reference to the original list [1, 2, 3].

So when y is printed to the console, it prints [1, 2, 3].

📖

Questions for: Variables