Discussion 1: Functions

Ice Breaker

Everyone say your name and some activity you enjoy doing outside. For each activity, ask if anyone else in your group likes to do that too. (Optional: after discussion you could make plans to go do one of these activities together.)

Then, each person share an expression that people say when they really like something, such as "awesome" or "nice one" or "that's tuff." Each person should try to come up with a different expression. Feel free to ask your group for help if you're stuck. You can even use other languages than English. Then, during the discussion, if someone says or does something well, use your expression!

Functions

Functions (such as pow) are called using call expressions (such as pow(10, 3) which returns 1000; 10 to the third power). The body of a function can print or return values (or both).

When print is called anywhere, its arguments are displayed right away.
Executing a return statement stops the function call and provides the value for its call expression.
When the end of a function body is reached without a return, the function returns None.

Tip: If a value needs to be used by code outside of a function, then return the value (instead of printing it).

Q1: Multiply

Implement multiply, which takes two numbers x and y. It prints out an equation showing the result of multiplying x and y, then returns the result.

Try to multiply numbers together just once in the body of multiply so that the Python interpreter doesn't have to perform multiplication more times than necessary (pun intended).

def multiply(x, y):
    """Multiply x by y and print what happened.

    >>> multiply(3, multiply(multiply(4, 5), 6))
    4 * 5 = 20
    20 * 6 = 120
    3 * 120 = 360
    360
    """

Hint 1: Printing an equation (at the end)

Q2: Cut One Out

Implement cut, which takes non-negative integers n and k and has only a return statement in its body. It returns a positive integer with all of the digits of n except the digit that is k positions to the left of the rightmost digit (the one's digit). If k is 0, then it returns n without its one's digit. If there is no digit of n that is k positions to the left of the rightmost digit, then it returns n.

def cut(n, k):
    """Return n with the kth digit from the right removed.

    >>> cut(3579, 2)
    379
    >>> cut(3579, 0)
    357
    >>> cut(3579, 1)
    359
    >>> cut(3579, 5)
    3579
    """
    return ____

Please don't look at the hint until everyone in your group agrees that you're stuck and need some extra help.

Hint 2 (at the end)

Hints

Hint 1: Printing an equation

Calling print on multiple arguments displays those values separated by spaces. For example, the call expression print(1, '+', 2, '=', 3) displays 1 + 2 = 3.

Hint 2

To implement a function, it can be helpful to open a Python interpreter and focus on an example. Here are all the pieces you need to put together to solve this problem for the example n=3579 and k=2.

>>> n = 3579
>>> k = 2
>>> pow(10, k)
100
>>> pow(10, k + 1)
1000
>>> n // 1000
3
>>> 3 * 100
300
>>> 3579 % 100
79
>>> 300 + 79
379