CSE 111 | Team Activity

W04 Team Activity: Lists

Instructions

Work as a team as explained in the instructions for the Week 02 team activity.

Purpose

There are a few details about writing and calling functions in Python that, if you understand, will help you be a more effective programmer. These details include default parameter values and pass by reference. As a team during this activity, you will write and call a function that demonstrates both default parameter values and pass by reference.

Helpful Documentation

The Python programming language allows a programmer to specify a default value for a function parameter. When a parameter has a default value, the corresponding argument is optional. The preparation content for lesson 4 includes a section about default parameter values.
Within a Python program, when a number is passed as an argument to a function, the computer copies the number from the argument into the parameter. In other words, the parameter gets a copy of the value that is in the argument. Copying the value of an argument into a parameter is known as pass by value.

In Python, when a list is passed as an argument to a function, the computer does not copy the list. Instead, the computer copies a reference to the list into the parameter. This means the argument and parameter refer to the same list. Copying a reference from an argument into a parameter is known as pass by reference. With pass by reference, if a called function changes a list that was passed to the function, this will of course change the list in both the calling and called functions because both the argument and parameter refer to the same list.

The preparation content for this week includes a section about passing arguments by value and by reference.
The Python random module contains functions to generate pseudo random numbers. The random.uniform function generates random floating-point numbers.
The Python random module contains a function named choice that randomly chooses one element from a list.
The built-in Python round function rounds a number to a specified number of digits after the decimal place.

Assignment

As a team, write a Python program named random_numbers.py that creates a list of numbers, appends more numbers onto the list, and prints the list. The program must have two functions named main and append_random_numbers as follows:

main
1. Has no parameters
2. Creates a list named numbers like this:
  numbers = [16.2, 75.1, 52.3]
3. Prints the numbers list
4. Calls the append_random_numbers function with only one argument to add one number to numbers
5. Prints the numbers list
6. Calls the append_random_numbers function again with two arguments to add three numbers to numbers
7. Prints the numbers list
append_random_numbers
1. Has two parameters: a list named numbers_list and an integer named quantity. The parameter quantity has a default value of 1
2. Computes quantity pseudo random numbers by calling the random.uniform function.
3. Rounds the quantity pseudo random numbers to one digit after the decimal.
4. Appends the quantity pseudo random numbers onto the end of the numbers_list.

At the bottom of your program, write an if statement that calls the main function. Then run your program and verify that your program works correctly.

Core Requirements

Your program includes two functions named main and append_random_numbers. The append_random_numbers function has two parameters named numbers_list and quantity, and quantity has a default value of 1.
The main function calls append_random_numbers twice, first with one argument and second with two arguments.
The append_random_numbers function includes a loop that appends quantity random numbers at the end of numbers_list.

Stretch Challenges

If your team finishes the core requirements in less than an hour, complete one or more of these stretch challenges. Note that the stretch challenges are optional.

Add a function named append_random_words that meets the following criteria:
1. Has two parameters: a list named words_list and an integer named quantity. The parameter quantity has a default value of 1
2. Randomly selects quantity words from a list of words and appends the selected words at the end of words_list.
Add statements in the main function that create a list of words, call the append_random_words function, and then print the list of words.
Add something or change something in your program that you think would make your program better, easier for the user, more elegant, or more fun. Be creative.

Testing Procedure

Verify that your program works correctly by following each step in this testing procedure:

Download the test_random_numbers.py Python file and save it in the same folder where you saved your random_numbers.py program. Run the test_random_numbers.py file and ensure that the test_random_numbers function passes. If it doesn’t pass, there is a mistake in your random_numbers function. Read the output from pytest, fix the mistake, and run test_random_numbers.py again until the test function passes.
```
> python test_random_numbers.py
=================== test session starts ====================
platform win32--Python 3.8.6, pytest-6.1.2, py-1.9.0, pluggy
rootdir: C:\Users\cse111\week04
collected 1 item
test_random_numbers.py::test_random_numbers PASSED    [100%]
==================== 1 passed in 0.11s =====================
```
Run your program and ensure that your program’s output is similar* to the output below.
```
> python random_numbers.py
numbers [16.2, 75.1, 52.3]
numbers [16.2, 75.1, 52.3, 84.2]
numbers [16.2, 75.1, 52.3, 84.2, 99.5, 20.4, 25.3]
words ['join', 'love', 'smile', 'love', 'cloud', 'head']
```
- Because your program is appending random numbers to the numbers list, your program’s output will be slightly different than the output shown above. Specifically, the last four random numbers and the random words will be different.

Sample Solution

Please work diligently with your team for the one hour meeting. After the meeting is over, please compare your solution to the sample solution. Please do not look at the sample solution until you have either finished the program or diligently worked for at least one hour. At the end of the hour, if you are still struggling to complete the assignment, you may use the sample solution to help you finish.

Ponder

Look again at the append_random_numbers function (and the append_random_words function if you wrote it for the stretch challenge). The first parameter, numbers_list, is a list. Recall that in Python, lists are passed by reference which means that any changes made to the list in the append_random_numbers (and append_random_words) function will change the list in main. You can verify this is true by looking at the output of your program. The numbers that were appended onto the list by the append_random_numbers function are stored in the same list in main.

Submission

When you have finished your team meeting, you are welcome to continue working on your own. Feel free to include that additional work when you report on your progress in Canvas.

When you are finished:

Return to Canvas to take the quiz.

Up Next

W04 Project Milestone: Chemistry