← return to practice.dsc10.com

This quiz was administered in-person. It was closed-book and closed-note; students were not allowed to use the DSC 10 Reference Sheet. Students had 20 minutes to work on the quiz.

This quiz covered Lectures 1-4 of the Winter 2024 offering of DSC 10.

Note (groupby / pandas 2.0): Pandas 2.0+ no longer silently drops columns that can’t be aggregated after a groupby, so code written for older pandas may behave differently or raise errors. In these practice materials we use .get() to select the column(s) we want after .groupby(...).mean() (or other aggregations) so that our solutions run on current pandas. On real exams you will not be penalized for omitting .get() when the old behavior would have produced the same answer.

Problem 1

Select all the true statements below.

• Mixing ints and floats in an arithmetic expression will always result in a float.

• Dividing two ints will sometimes result in an int.

• Any float can be converted to a string using the function str().

• Any string can be converted to a float using the function float().

Problem 2

Consider the assignment statement below.

pear = [6, 10.1, "pear", 13]

What does the expression np.array(pear) evaluate to?

• array([6, 10.1, "pear", 13])

• array([6, 10.1, pear, 13])

• array(["6", "10.1", "pear", "13"])

• array(["pear"])

• array([pear])

• This expression errors

Problem 3

Suppose x and y are both ints that have been previously defined, with x < y. Now, define:

peach = np.arange(x, y, 2)

Say that the spread of peach is the difference between the largest and smallest values in peach. The spread should be a non-negative integer.

Problem 3.1

Using array methods, write an expression that evaluates to the spread of peach.

Problem 3.2

Without using any methods or functions, write an expression that evaluates to the spread of peach.
Hint: Use [ ].

Problem 3.3

Choose the correct way to fill in the blank in this sentence:

• always less than

• sometimes less than and sometimes equal to

• always greater than

• sometimes greater than and sometimes equal to

• always equal to

Problem 4

Suppose fruits is a DataFrame of the fruits Ashley bought at the grocery store, where:

• The "fruit" column contains the name of the fruit, as a string. All values in this column are distinct.

• The "price" column contains the amount in dollars spent on the fruit, as a float.

• The "pounds" column contains the number of pounds purchased, as an int.

Problem 4.1

Fill in the blanks below to add a new column to fruits called "price_per_ounce" that contains the price per ounce of each of the fruits in fruits. There are 16 ounces in a pound.

    fruits = fruits.__(x)__(price_per_ounce = __(y)__ / __(z)__)

Problem 4.2

Write a line of code that evaluates to the amount of money, in dollars, that Ashley spent on fruit at the grocery store.

Problem 4.3

Fill in the blanks so that the expression below evaluates to the name of the fruit with the highest price per ounce.

    (fruits.sort_values(by = "price_per_ounce", ascending = __(x)__)
           .get(__(y)__).iloc[0])

Problem 4.4

Assuming that "mango" is one of the fruits Ashley bought, fill in the blanks so that the expression below evaluates to the price per ounce of "mango".

    fruits.__(x)__("fruit").get("price_per_ounce").__(y)__["mango"]

👋 Feedback: Find an error? Still confused? Have a suggestion? Let us know here.