Question

Write and test a function to meet this specification. sumList (nums) nums is a list of numbers. Returns the sum of the numbers in the list.

Short answer

Define `sumList` function; iterate and accumulate total; finally return the sum.

Step-by-step solution

Define the Function

The first step is to define a Python function named `sumList` that takes one parameter, `nums`, which is expected to be a list of numbers. The function will be written using the `def` keyword in Python.

Initialize the Sum Variable

Inside the function, initialize a variable `total` to 0. This variable will keep track of the accumulating sum of the numbers in the list.

Iterate Through the List

Use a `for` loop to iterate through each element in the list `nums`. For each iteration, the loop will add the current number to the `total` variable.

Update the Total Sum

In each iteration of the loop, update the `total` variable by adding the current number to it. This can be done with the expression `total += num` where `num` is the current number in the loop.

Return the Final Sum

After the loop has processed all elements in `nums`, the final sum is stored in the `total` variable. Use the `return` statement to return this value from the function.

Test the Function

Write test cases to ensure the function works as expected. For example, check edge cases such as an empty list, a list with one element, and a list with various positive and negative numbers. Example test case: ``` print(sumList([1, 2, 3, 4, 5])) # Should output 15 print(sumList([-1, -2, -3])) # Should output -6 print(sumList([])) # Should output 0 ```

Key concepts

for loop

A `for` loop is an essential concept in Python that allows you to iterate over a sequence, such as a list or a string. In the context of the `sumList` function, the `for` loop is used to go through each element in the list `nums`. This loop enables us to access every item in the list, one at a time, which is crucial for performing operations like summing the elements.

When writing a `for` loop, we use the syntax `for element in sequence`. In this case, the sequence is our list `nums` and each `element` is a number in that list.

This simple yet powerful structure helps in performing repeated tasks efficiently. As the loop iterates, we can execute a block of code for each item, such as adding numbers in this example. It’s important to understand loops to handle data processing effectively.

return statement

The `return` statement is an integral part of functions in Python, signaling the end of a function and specifying what it should output. In the `sumList` function, the purpose of the `return` statement is to output the accumulated sum held in the `total` variable.

When Python encounters a `return` statement, it immediately stops executing the rest of the code in the function and 'returns' back to the calling environment, carrying the value specified. This mechanism allows the function to pass the result of its computation back to the point where it was invoked.

Understanding `return` is crucial because without it, our function wouldn't be able to send data back after completion. Remember, the function uses `return total` to finalize the process of summing the numbers, providing us with the final result of this operation.

list iteration

List iteration refers to the process of accessing each element in a list, often using loops. In the `sumList` function, list iteration is accomplished through the `for` loop, which systematically steps through each number in the list `nums`.

Iteration is fundamental because lists are possibly one of the most used data structures in programming due to their dynamic nature and versatility. By iterating over a list, we can perform tasks like arithmetic operations, data transformations, or filter through elements.

By iterating through the list, the function continuously updates the `total` by adding each number one by one. This approach ensures that every number is included in the final sum, making list iteration a core practice in efficiently handling data within lists in Python.

testing functions

Testing functions is a critical practice to ensure that your code performs as expected. For the `sumList` function, testing involves executing the function with various input lists to verify its correctness under different scenarios.

Some key aspects to consider when testing functions include:

• Edge Cases: Test with an empty list to see if the function returns `0` as expected.
• Simple Cases: Use a list with one number to check if the output is that number itself.
• Complex Cases: Include lists with a variety of positive and negative numbers to ensure that the function accurately calculates the sum.

By implementing tests in this manner, you can catch bugs early and make sure your function performs reliably in diverse circumstances. Practicing good testing habits enhances the robustness and reliability of your code, especially as complexities grow.