4.7. Functions, loops, and types assignment¶

Note

This assignment is available as an Ipython notebook (.ipynb)

In this assignment we review basic concepts of containers, loops, and functions.

4.7.1. Exercise 1¶

We do the first exercise as an example. Suppose:

>>> a_list = [2,7,8, 19]
>>> YOUR CODE HERE
2

The idea is to write the line of code that will produce the given output, 2 in this case. It should this be an expression that operates on a_list. A simple correct answer is:

>>> a_list = [2,7,8, 19]
>>> a_list[0]
2

4.7.2. Exercise 2¶

Suppose:

>>> a_list = [2,7,8, 19]
>>> YOUR CODE HERE
19

Write the line of code that produces the given output.

4.7.3. Exercise 3¶

Suppose:

>>> a_list = [2,7,8, 19]
>>> YOUR CODE HERE
[7,8]

Write the line of code that produces the given output.

4.7.4. Exercise 4¶

Suppose:

>>> a_list = [2,7,8, 19]
>>> YOUR CODE HERE
[3,8,9,20]

Write the line of code that produces the given output. [Hint: Try a list comprehension]

4.7.5. Exercise 5¶

Suppose:

>>> a_list = [2,7,8, 19]
>>> YOUR CODE HERE
[True, True, False, False]

Write the line of code that produces the given output. [Hint: Try a list comprehension that collects a list of the results of a Boolean test]

4.7.6. Exercise 6¶

Write a for loop that collects all the words in a list that are three letters long and places them in a list named result.

Here is a list to work on:

>>> test_list = ['the', 'be', 'of', 'and', 'a', 'in', 'to', 'have', 'it',
                 'to', 'for', 'I', 'that', 'you', 'he', 'on', 'with', 'do',
                 'at', 'by', 'not', 'this', 'but', 'from', 'they', 'his']

Note This can be done as a list comprehension and you are welcome to do it that way.

4.7.7. Exercise 7¶

Now, using the same test_list as in exercise 6, write a for loop that counts the number of words that are three letters long in test_list and places the result in a variable named three_let_word_freq. You can do this by just taking the length of the list you computed in exercise 7, but try to do it without building that list. Just use a variable whose value is an integer representing the number of three letter words seen thus far and increment it by one each time you see a three-letter word.

4.7.8. Exercise 8¶

Write a for loop that finds the item which occurs most frequently in a list of items. You can use the following list as an example:

L = ['1', '4', '1', '5', '9', '2', '6', '5', '3', '5',
     '8', '9', '7', '9', '3', '1', '1', '6']

You will need a dictionary and it will be most convenient to use a Counter. It will be helpful to review our discussion of Counters in Section Dictionaries. It will also be helpful to read the Python docs to find a convenient method that finds the element in a counter with the highest count.

4.7.9. Exercise 9¶

Write a function that adds 1 to any number. Here is how it should work:

>>> x = add1(2)
>>> x
3

Hint: If you’re having trouble getting this behavior, maybe you forgot about return?

4.7.10. Exercise 10¶

Write a function that converts temperatures (as numbers) from Fahrenheit to Celsius scale. Here is how it should work:

>>>  C = fahrenheit_to_celsius(212)
>>>  C
100.0
>>>  C = fahrenheit_to_celsius(-40)
>>>  C
-40.0
>>>  C = fahrenheit_to_celsius(32)
>>>  C
0.0

Write a function that converts temperatures (as numbers) from Fahrenheit to Celsius scale. Here is how it should work:

>>>  C = fahrenheit_to_celsius(212)
>>>  C
100.0
>>>  C = fahrenheit_to_celsius(-40)
>>>  C
-40.0
>>>  C = fahrenheit_to_celsius(32)
>>>  C
0.0

4.7.11. Exercise 11¶

Write a function that computes the volume of a cone. Note that if V is the volume of a cone, and h is its height and r is the radius of the base, then

$V = \frac{1}{3} \pi r^{2} h$

Here is how the function should work:

>>>  V = cone_volume(2,3)
>>>  V
37.69911184307752