Checklist 02

This is a general outline of the key concepts (arranged by topic) that you should know for Exam 02.

Format

The exam will have the following format:

  1. Short Answers: Briefly answer questions about

  2. Translations: Convert Unix pipelines to Python code (7 Points).

Part 1 is to be done first on paper. After this part is completed, part 2 can be done with the aid of your laptop and the Internet (but not other people).

Representative, but not Exhaustive

This check list is meant to be representative, rather than exhaustive (ie. there may be questions that show up on the exam that are not shown below).

Data Processing

Concepts

  1. How is Python different from the Bourne shell? How is it similar?

  2. How do we manage control flow in Python? How do we utilize these constructs?

    • Conditionals

    • Loops

    • Exceptions

    • Functions

  3. What data structures do we have in Python? What are their basic operations? When would we want to use each type of data structure?

    • Lists / Tuples

    • Dictionaries / Sets

  4. How do we do the following in Python?

    • Process command-line arguments

    • Read and write files

    • Read standard input

    • Access environment variables

    • Change the case of a string

    • Split a string, combine a list of strings

    • Slice a list

    • Execute an external command

    • Process JSON data from the web

    • Sort lists and dictionaries

    • Count with dictionaries

Sample Questions

Code Snippets

Write Python code snippets to perform the following tasks (don't worry about she-bangs or imports):

  1. Print out each element of a list (one element per line).

  2. Print the contents of stdin (line-by-line).

  3. Print the first 10 items of a list.

  4. Print the length of a list.

  5. Print the largest and smallest elements of a list.

  6. Print the first and last words in the string "Let this promise in me start, Like an anthem in my heart".

  7. Print the results of the ps aux command.

  8. Print the contents of a specific webpage.

Code Evaluation

Given the following data:

comics = {
    "marvel": ["deadpool", "spider-man", "wolverine"],
    "dc"    : ["batman", "superman"]
}

For each of the following expressions, state the output value:

  1. len(comics)

  2. list(comics.keys())[0]

  3. list(comics.values())[-1]

  4. comics['marvel'][1]

  5. comics['dc'][-1][-3:]

Translation

Given the following Unix pipelines, write Python code that accomplishes the same task.

Note: No credit will be given for simply calling os.system on the given pipeline. You may use os.popen to read the output of one command, but you may not use a pipeline.

  1. cat /etc/passwd | cut -d : -f 1 | grep d$ | wc -l

  2. cat /etc/passwd | cut -d : -f 3 | grep -E '^[0-9]{2}$' | sort | uniq

  3. curl -sLk http://yld.me/raw/lmz | cut -d , -f 1 | grep -Eo '^[^jfs].*'

  4. curl -sLk http://yld.me/raw/lmz | cut -d , -f 2 | grep -Eo '^B.*' | sort

  5. who | sed -rn 's|.*\((.*)\).*|\1|p' | sort | uniq

  6. ls -l /etc | awk '{print $2}' | sort | uniq -c

Functional Programming

Concepts

  1. What is the difference between procedural and functional programming?

  2. How do we use map, filter, and lambda to do functional programming in Python?

List Comprehensions

Concepts

  1. How do we use list comprehensions in Python?

Generators

Concepts

  1. What is an iterator and how is it different from a list?

  2. What is a generator and how it is different from a list?

  3. How do we use common iterators and generators such as:

Concurrency and Parallelism

Concepts

  1. What is the difference between concurrency and parallelism?