PCEP Certification Practice Test: Understanding the None Keyword in Python
PCEP Certification Practice Test - Questions, Answers and Explanations
Below is a set of 25 questions for the Certified Entry-Level Python Programmer (PCEP) examination focusing on the subtopic "the None keyword." The questions use various formats, including single- and multiple-select questions, fill-in-the-gap, code fill, code insertion, sorting, and more.
Question 1: What does the None keyword represent in Python?
- It represents a value of zero.
- It represents a string "None".
- It represents the absence of a value.
- It represents a boolean True.
Answer: C) It represents the absence of a value.
Explanation: In Python, None represents the absence of a value or a null value, similar to null in other programming languages.
Question 2: Which of the following are true about the None keyword? (Choose all that apply)
- It is used to represent the absence of a value.
- It is a built-in constant in Python.
- Functions that do not return anything implicitly return None.
- None can be used as a placeholder value in variables or functions.
Answer:
- It is a built-in constant in Python.
- It is used to represent the absence of a value.
- Functions that do not return anything implicitly return None.
- None can be used as a placeholder value in variables or functions.
Explanation: None is a built-in constant used to indicate the absence of a value and is commonly returned by functions that do not have a return statement.
Question 3: Complete the code to check if the variable result is equal to None.
result = None if result ______ None: print("Result is None")▼
Answer: is
Explanation: In Python, is is used to compare an object to None because None is a singleton, meaning there is only one instance of None in memory.
Question 4: What will be the output of the following code?
def do_nothing(): pass result = do_nothing() print(result)
- None
- do_nothing
- 0
- Error
Answer: A) None
Explanation: Since the do_nothing() function does not return anything, it implicitly returns None, which is then printed.
Question 5: Insert the correct code to check if the function check_value returns None.
def check_value(): pass if ______: print("Function returned None")▼
Answer: check_value() is None
Explanation: You can check if the return value of check_value() is None using check_value() is None.
Question 6: What will the following code output?
value = None print(type(value))
- <class 'NoneType'>
- None
- <class 'None'>
- Error
Answer: A) <class 'NoneType'>
Explanation: The type of None is NoneType, which is the data type representing the absence of a value in Python.
Question 7: Which of the following situations would result in a function returning None? (Choose all that apply)
- A function that has no return statement.
- A function with an empty return statement.
- A function that returns the value None.
- A function that raises an exception.
Answer: A) A function that has no return statement.
B) A function with an empty return statement.
C) A function that returns the value None.
Explanation:Functions with no return statement or an empty return return None implicitly. A function can also explicitly return None.
Question 8: Arrange the steps to correctly define a function that returns None when called.
- Use the return keyword without any value.
- Define the function.
- Call the function.
- Check if the return value is None.
Answer: 2, 1, 3, 4
Explanation: First, define the function, then use the return keyword without a value to return None. After calling the function, check if the return value is None.
Question 9: Complete the code to explicitly return None from the function no_result.
def no_result(): ______ None▼
Answer: return
Explanation: The return statement can be used to explicitly return None from a function.
Question 10: What will be the output of the following code?
def check(): return None result = check() print(result is None)
- True
- False
- None
- Error
Answer: A) True
Explanation: The function check() returns None, and the expression result is None evaluates to True.
Question 11: Insert the correct code to return None when the condition is false.
def check_condition(condition): if not condition: ______ return "Condition is True"▼
Answer: return None
Explanation: You can explicitly return None when the condition is False by using the return None statement.
Question 12: What is the return type of the following function?
def example(): pass
- None
- <class 'NoneType'>
- int
- str
Answer: B) <class 'NoneType'>
Explanation: The example() function has no return statement, so it returns None. The type of None is NoneType.
Question 13: Which of the following code snippets will explicitly return None? (Choose all that apply)
- def f(): return None
- def f(): pass
- def f(): return
- def f(): return 0
Answer:A) def f(): return None
B) def f(): pass
C) def f(): return
Explanation: return None, pass, and an empty return statement all cause the function to return None. Only Option D explicitly returns 0.
Question 14: Arrange the steps to create a function that returns a result if the condition is true, and None if the condition is false.
- Check the condition.
- Define the function.
- Return None if the condition is false.
- Return the result if the condition is true.
Answer: 2, 1, 3, 4
Explanation: First, define the function, check the condition, return None if the condition is false, and return the result if the condition is true.
Question 15: Complete the code to return None when the condition is not met.
def evaluate(condition): if not condition: return ______ return "Valid condition"▼
Answer: None
Explanation: The function should return None when the condition is not met, indicating the absence of a value.
Question 16: What will be the output of the following code?
def return_none(): return None print(type(return_none()))
- <class 'NoneType'>
- None
- <class 'int'>
- Error
Answer: A) <class 'NoneType'>
Explanation: The return_none() function explicitly returns None, and the type of None is NoneType.
17. Insert the correct code to check if a variable x is None.
x = None if x ______: print("x is None")▼
Answer: is None
Explanation: Use is None to check if a variable is None, as None is a singleton in Python.
Question 18: What is the value of x after the following code is executed?
x = None if x is None: x = 10
- None
- 10
- Error
- 0
Answer: B) 10
Explanation: Since x is initially None, the condition x is None evaluates to True, and x is assigned the value 10.
Question 19: Which of the following are correct ways to check if a variable is None? (Choose all that apply)
- if x == None:
- if x is None:
- if x != None:
- if x is not None:
Answer: B) if x is None:
D) if x is not None:
Explanation: The correct and recommended way to check if a variable is None is by using is None or is not None. Using == or != is not considered best practice.
Question 20: Arrange the steps to define a function that returns None and verify its type.
- Use the return keyword with None.
- Define the function.
- Call the function.
- Check the type of the return value.
Answer: 2, 1, 3, 4,
Explanation: First, define the function, use the return None statement, call the function, and finally check the type of the returned value.
Question 21: Complete the code to assign None to the variable value.
value = ______▼
Answer: None
Explanation: The keyword None is assigned to value, indicating the absence of a value.
Question 22: What will be the output of the following code?
def func(): return result = func() print(result is None)
- True
- False
- None
- Error
Answer: A) True
Explanation: The function func() has an empty return statement, which implicitly returns None. Therefore, result is None evaluates to True.
Question 23: Insert the correct code to check if the result of the function func is not None.
def func(): return None if func() ______: print("Function did not return None")▼
Answer: is not None
Explanation: To check if the function result is not None, use is not None.
Question 24: What will be the result of the following code?
def do_something(): pass result = do_something() print(result)
- None
- pass
- Error
- 0
Answer: A) None
Explanation: The do_something() function contains the pass statement, meaning it does nothing and implicitly returns None.
Question 25: Which of the following statements about None are correct? (Choose all that apply)
- A function with no return statement returns None.
- None represents the absence of a value.
- The type of None is NoneType.
- You can compare None with is None.
Answer:
- None represents the absence of a value.
- The type of None is NoneType.
- A function with no return statement returns None.
- You can compare None with is None.
Explanation: All the provided statements about None are correct.
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