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Return: Quiz I in Python - Time Complexity: O(1)


Quiz: What would this code produce if we were to copy-paste it in a code editor and run it?

def get_double(n):
	n * 2

result = get_double(10)
print(result)

Options:

  • A: It would print 20

  • B: It would print None

  • C: It would produce errors

  • A: It would print 10

Important Note:

Do not use an actual code editor to get the answer! It would defy the whole purpose of the quiz!

Instructions:

Pick your answer and assign variable answer in the code editor with that answer.

For example, if you think the answer to the quiz is B, write answer = "B" in the code editor and press Validate Solution!.

Understanding the Problem

The core challenge of this problem is to understand the behavior of the Python function and its return value. The function get_double is supposed to double the input value n, but it lacks a return statement. This is a common pitfall in Python programming where a function without an explicit return statement returns None by default.

Approach

To solve this problem, we need to analyze the given code step-by-step:

  1. Define the function get_double which takes an argument n.
  2. Inside the function, the expression n * 2 is evaluated but not returned.
  3. Call the function with the argument 10 and store the result in the variable result.
  4. Print the value of result.

Since the function does not have a return statement, it will return None by default. Therefore, the output of the code will be None.

Algorithm

Here is a step-by-step breakdown of the algorithm:

  1. Define the function get_double with a parameter n.
  2. Inside the function, evaluate the expression n * 2.
  3. Since there is no return statement, the function will return None.
  4. Call the function with the argument 10 and assign the result to the variable result.
  5. Print the value of result, which will be None.

Code Implementation

def get_double(n):
    # The function multiplies n by 2 but does not return the result
    n * 2

# Call the function with 10 and store the result in 'result'
result = get_double(10)

# Print the result, which will be None
print(result)

Complexity Analysis

The time complexity of this function is O(1) because it performs a constant amount of work regardless of the input size. The space complexity is also O(1) as it uses a fixed amount of space.

Edge Cases

Since the function does not return any value, the only edge case to consider is the default return value of None. Any input to the function will result in None being returned.

Testing

To test this solution, you can use the following test cases:

# Test case 1: Input is 10
result = get_double(10)
print(result)  # Expected output: None

# Test case 2: Input is 0
result = get_double(0)
print(result)  # Expected output: None

# Test case 3: Input is -5
result = get_double(-5)
print(result)  # Expected output: None

Thinking and Problem-Solving Tips

When solving such problems, always ensure that your functions have explicit return statements if you expect them to return a value. This helps avoid common pitfalls and makes your code more predictable and easier to debug.

Conclusion

In this blog post, we analyzed a simple Python function and understood why it returns None instead of the expected value. We discussed the importance of return statements and provided a detailed explanation of the algorithm, code implementation, and complexity analysis. Understanding these concepts is crucial for writing effective and bug-free code.

Additional Resources