CS 320 midterm 1

virtual machine

"fake" machine running on physical machine allows us to run additional operating systems

function to split string into a list by spaces

.split()

Function to remove spaces at the beginning and end of a string

.strip()

When programming, how can you fix the issue that different OSs represent file paths differently? (\ for windows vs / for mac)

1. Tell anybody reproducing your results to use the same OS 2. Use the OS python backage to open file f=open(os.path.join("data", "file.txt"))

use cases of a version control system

1. Troubleshoot a bug 2. Tag "good" commits to create releases 3. Get/give feedback

Jobs of an operating system

1. allocation => assigns processing power (resources of CPU) for different processes 2. Abstraction => does "inconvenient" tasks (like interact with the hard drive)

how to use check_output to run a command with arguments

1. check_output("git --version", shell=TRUE) 2. (preferred) check_output(["git", "--version"])

steps to tag a commit

1. checkout the commit you want to tag/release 2. git tag <name of tag>

two ways to create a repository

1. copy it from a host like GitHub with git clone 2. make an empty one with git init

Is "in" faster on a list or a set?

A set

detached head state

HEAD is not pointing to a branch, it's pointing to a commit (even if it's the same commit as another branch)

Is HEAD a branch?

No. It shows where you are currently

what does the .git file contain?

Prior commits with other versions of the file

if all CPUs had the same instruction set, would we still need a Python interpreter?

Yes, you would still need it. You still need to convert high-level code into machine code

address space

a big "list" of bytes, per process, for all state

repository

a directory/folder on your computer that records a commit history

branch

a label attached to a commit that re-attaches to new commits

HEAD

a label for the current commit

tag

a long-term label associated with a commit

process

a running program

commit

a snapshot of files at a point in time - users manually run commands to preserve good versions

compiler

a tool for running the same code on different CPUs -- like an interpreter but happens before the program runs

what type of variable does check_output return?

byte object convert to string like this: str_output = str(output, encoding="utf-8")

CPU

chip that executes instructions, tracks position in code

conflict

differences that cannot automatically be merged

How to install a specific version of a dependency

ex: pip install pandas==0.25.1 - if you don't specify it will default to the latest stable version

What is a byte object?

example of a sequence - list, str, tuple are also sequences features: - indexing: seq[index] - slicing: seq[start index: exclusive end index] - iteration: for val in seq: - length: length(seq) - existence: <val> in seq

create a new branch without immediately checking out

git branch <branch name>

how to create and checkout a new branch

git checkout -b <name>

checkout an already existing branch

git checkout <branch name>

ghost commit

happens when you are in a detached head state and you make another commit; it will not update to a branch and will get lost in history - can be accessed with git checkout <commit number>

abstraction

hiding inconvenient details with something easier to use

address

index in the address space

byte

integer between 0 and 255

How does python fix the problem of different CPUs having different instruction sets? - program may not "fit" CPU

interpreters

git branch

list your branches. a * will appear next to the currently active branch

reproducibility

others can run our analysis code and get the same results

instruction set

pairing of CPU instructions/operatioins with numeric codes

encoding

pairing of characters with numeric codes

cloud

place where you can rent virtual machines and other services

check pandas version

print(pandas.__version__)

git restore <file>

restores file to last commit

ssh

secure shell -- tool that lets you remotely access another machine

how do you open documentation about a function inside jupyter?

shift+tab after entering the function name

operating system

software that allocates+abstracts resources

access the first argument in python

sys.argv[0] - will be the file name (different than C!) for example, it would be fileName.py for "python3 fileName.py"

allocation

the giving of a resource to a process

what does time.time() return?

the number of seconds elapsed since January 1st, 1970

resource

time on CPU, space in memory, space on SSD, etc.

merge

to combine changes on another branch into the current branch

interpreters (like python.exe)

translates human code to machine code for your CPU - makes it easier to run the same code on different machines

git diff

what changes have been made to repository (before commit)

how can you run a command in python and see the output?

with check_output from subprocess ex: from subprocess import check_output output = check_output("pwd")