Description
Assignment
This assignment should be completed as a single Python source (.py) file modified from
hw4-template.py (available on Carmen). Each question (including the Challenge Activities)
has an associated TODO comment in the template file.
Argument Types. In this section, we’ll explore the different argument types permitted by Python.
Each function you write should simply print the name and value of every argument passed to the
function by the caller.
(1) The function printargs0 is implemented and takes a number of arguments. Write a
statement that calls this function.
(2) Write a function called printargs1 that takes four arguments, all with default values,
and call it.
(3) Write a function called printargs2 that takes one positional-only argument, two
positional-or-keyword arguments, and three keyword-only arguments, and call it.
(4) Write a function called printargs3 that takes four positional-only arguments, and call it.
(5) Write a function called printargs4 that takes a variadic argument list, and call it.
(6) Write a function called printargs5 that takes a keyword-variadic argument, and call it.
Dictionaries. In this section, you’ll explore dictionaries and their many uses.
(7) Write a function called build_dict1(keys, values) that, given two lists of equal
length returns a dictionary in which each item in keys is associated with the corresponding
item in values. Use a for-in loop to do so.
(8) Write a function called build_dict2(keys, values) that has the same behavior as build_dict1, but does not use a loop. Specifically, your implementation of
build_dict2 should use a dictionary comprehension.
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(9) Write a function called build_dict3(keys, values) that has the same behavior as
build_dict1 and build_dict2, but uses neither a loop nor a comprehension. Specifically, your implementation of build_dict3 should use the built-in zip(seq1, seq2)
function that produces a sequence consisting of pairs of corresponding items from seq1 and
seq2.
(10) Write a function called letter_freq(s: str) -> dict that, given a string s, returns
a dictionary which maps each letter to the number of times it appears in the string. The
function should be case-insensitive, but the dictionary keys should be uppercase letters. If a
letter does not appear in the string, it should not appear in the returned dictionary. Hint:
use the functions str.isalpha(), str.isupper(), or str.islower() to identify
letters in s.
(11) Write a function called popular_letter(s: str) -> str that, given a string s, returns the letter in that string that appears most often. Hint: use the letter_freq function you just created as well as the built-in max function (see https://docs.python.
org/3/library/functions.html#max).
Generators and Lambdas. In this section we’ll both build and use generators and lambda expressions.
(12) Write a generator function called collatz(x) that generates the series identified by the
Collatz Conjecture starting with value x. That is, it should generate the next number in the
series based on the following equation (the series is sometimes called a “Hailstone Series”):
Cn`1 “
$
’’&
’’%
Cn{2 Cn is even
Cn ˚ 3 ` 1 Cn is odd
Note: we say the series is terminated when its value is 1. Think about why that is the case.
(13) Write a function called collatz_len(x) that returns the length of the series generated
by collatz(x).
(14) Write a generator function called words(s) that iterates through every “word”
(i.e., contiguous sequence of letter characters) in a string. For example, when
s == “Hello, this is Alan.”, the generator should produce the strings “Hello”,
“this”, “is”, and “Alan” in order.
(15) Write a function called mapped_list(lst, f) that returns a new list that is the result
of applying the single-argument function f to each item in lst.
(16) Call mapped_list with a lambda expression such that the created list consists of the
length of the Collatz Conjecture series (as defined above in #12) generated by each element
of lst.
Challenge Activities
Some homeworks (such as this one) will have additional challenge activities. These activities do
not contribute to your grade, but they are problems that I find interesting or challenging.
(17) The mcg function is an exceptionally simple pseudorandom number generator. Play with
the apparently-arbitrary values in the function. Can you make the results noticeable better
or worse by chaning them?
(18) The diceroller function on the slides is fine, but the output leaves something to be
desired. Modify the diceroller function so that the output is a horizontal bar graph
made of ASCII characters. Do not import any charting modules—only use built-in functions
for dict and str. A useful character to use as you build each bar is the Unicode character
‘FULL BLOCK’ (U+2588), which can be included in Python source as the str literal
u”\u2588″. Here are the requirements for your output:
‚ There should be one line for each possible roll value, and they should be sorted in
increasing order.
‚ Each line should begin with a label (i.e., a roll value) followed by at least one space,
followed by the bar for that value.
‚ Each bar should be left-aligned in the console.
‚ Each line should be no more than 80 characters wide, including the label.
(19) Use the generator you created in problem #14 to write a function called
firstlines(file_name) that builds a dictionary of every word that appears in a file
mapped to the line number on which it first appears. Hint: to read from a file, use the
built-in function open(file_name), which opens the file with an iterator over the lines
of that file. Each line of the file is provided as a str ending in a newline character “\n”.
Submission
To submit this assignment, upload your modified hw4-template.py file containing all of your
code and question answers to the “Homework 4” assignment on Carmen. If there are test cases in
your modified file, please comment them out before uploading it. As always, be sure to note all
group members who contributed to the assignment and what those contributions were.
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