Lab 2: Control

Due: Friday 09/11 @ 11:59pm
Points: 1
Download: lab02.zip

Attendance

You need to submit the lab problems in addition to attending to get credit for lab. Students in mega lab only need to submit the lab problems. Preceptor interviews are highly recommended but not required for lab submissions.

If you are in regular lab, your TA will come around during lab to check you in. If you didn't attend for a good reason (such as being sick), fill out this form (within 2 weeks of your lab): attendance form.

Required Questions

What Would Python Display? (WWPD)

Q1: WWPD: What If?

Predict what Python will display by running this unlocking session:

Hint: print (unlike return) does not cause a function to exit.

python3 -m pytest -k if_statements --unlock

Unlocking Examples

>>> def ab(c, d):
...     if c > 5:
...         print(c)
...     elif c > 7:
...         print(d)
...     print('foo')
>>> ab(10, 20)
______
______
>>> def bake(cake, make):
...     if cake == 0:
...         cake = cake + 1
...         print(cake)
...     if cake == 1:
...         print(make)
...     else:
...         return cake
...     return make
>>> bake(0, 5)
______
______
______
>>> bake(1, "yum")
______
______
>>> bake(2, 3)
______

Write Code

Q2: Falling Factorial

Let's write a function falling, which is a "falling" factorial that takes two arguments, n and k, and returns the product of k consecutive numbers, starting from n and working downwards. When k is 0, the function should return 1.

def falling(n, k):
    """Compute the falling factorial of n to depth k.

    >>> falling(6, 3)  # 6 * 5 * 4
    120
    >>> falling(4, 3)  # 4 * 3 * 2
    24
    >>> falling(4, 1)  # 4
    4
    >>> falling(4, 0)
    1
    """
    "*** YOUR CODE HERE ***"

python3 -m pytest -k falling

Q3: Divisible By k

Write a function divisible_by_k that takes positive integers n and k. It prints all positive integers less than or equal to n that are divisible by k from smallest to largest. Then, it returns how many numbers were printed.

def divisible_by_k(n, k):
    """Print all positive integers up to n that are divisible by k from smallest
    to largest, then return how many numbers were printed.

    >>> a = divisible_by_k(10, 2)  # 2, 4, 6, 8, and 10 are divisible by 2
    2
    4
    6
    8
    10
    >>> a
    5
    >>> b = divisible_by_k(3, 1)  # 1, 2, and 3 are divisible by 1
    1
    2
    3
    >>> b
    3
    >>> c = divisible_by_k(6, 7)  # There are no integers up to 6 that are divisible by 7
    >>> c
    0
    """
    "*** YOUR CODE HERE ***"

python3 -m pytest -k divisible_by_k

Q4: Double Eights

Write a function that takes in a number and determines if the digits contain two adjacent 8s.

def double_eights(n):
    """Return true if n has two eights in a row.
    >>> double_eights(8)
    False
    >>> double_eights(88)
    True
    >>> double_eights(2882)
    True
    >>> double_eights(880088)
    True
    >>> double_eights(12345)
    False
    >>> double_eights(80808080)
    False
    """
    "*** YOUR CODE HERE ***"

python3 -m pytest -k double_eights

Submit Assignment

Submit this assignment by running Provenance: Prepare Submission Bundle from the VS Code command palette and uploading the resulting zip to Gradescope. The zip already contains the files you've edited. Lab 00 has detailed instructions.

Your responses to WWPD questions are not submitted, and they do not need to be. Lab credit is based on the code writing questions.

Optional Questions

These questions are optional. If you don't complete them, you will still receive credit for this assignment. They are great practice, so do them anyway!

Q5: Sum Digits

Write a function that takes in a nonnegative integer and sums its digits. (Using floor division and modulo might be helpful here!)

def sum_digits(y):
    """Sum all the digits of y.

    >>> sum_digits(10) # 1 + 0 = 1
    1
    >>> sum_digits(4224) # 4 + 2 + 2 + 4 = 12
    12
    >>> sum_digits(1234567890)
    45
    >>> a = sum_digits(123) # make sure that you are using return rather than print
    >>> a
    6
    """
    "*** YOUR CODE HERE ***"

python3 -m pytest -k sum_digits