on 12-Oct-2018 (Fri)

Question

In python, you have sets, s={1,2,3} and t={1}, check (expect True) if all items in t are also in s.
Answer: s. [...] (t)

Answer

s.issuperset(t)

Question

In regular expressions, using grep, match for the words kremlin, krypton, krn, krzn, in file test.txt?

Answer

grep -w 'kr.*n' test.txt
^^ note the use of "." followed by "*" to search for 0 or more of any char

Question

In algorithms, between recurtion and iteration, which one is usually more processor intensive (hint: thing of case where it fails to terminate/is infinite)?

Answer

interation

Question

In algorithm, time complexity is measured in [...] notation

Answer

big-O
^^ FYI, O stands for Order-magnitude

Question

In algorithms, what is the big-O time complexity of an algorithm that shrinks the input size in half on each iteration (e.g. finding an element in a sorted array)?

Answer

O(logn)
^^ note that logn is, log base2 n

Question

In algorithms, what is the time complexity of iterating through all items in a single loop?

Answer

O(n)

Question

In algorithms, what is the big-O time complexity of merge sort?

Answer

O(nlogn)
^^ you are reducing the input size by half on each recursion cycle (so logn), and on each merge you are iterating through whole list (so n) so n*logn

Question

In algorithms, what is the big-O time complexity of an algorithm that has nested loops (loop within a loop)?

Answer

O(n^2)

Question

In algorithms, what is the big-O time complexity of an algorithm that has triple nested loop (loop in a loop in a loop)?

Answer

O(n^3)

Question

In python 2, what is the easy way to sort a list, using "sorted" method, using a custom comparison function (for example, how to sort release_numbers = [1.2, 4.4.4, 1.2.1], using custom "compare" function that compares 1.2 to 1.2.1)?

Answer

sorted(release_numbers, cmp=compare)
^^ note the cmp arg is unique to python 2 and takes a custom compare function to use in sort.

Question

In python 3, what is the easy way to sort a list, using "sorted" method, using a custom comparison function (for example, how to sort release_numbers = [1.2, 4.4.4, 1.2.1], using custom "compare" function that compares 1.2 to 1.2.1)?

Answer

sorted(release_numbers, key=functools.cmp_to_key(compare))
^^ note, in python 3, sorted does not have the cmp argument so you have to use the key argument via the functools.cmp_to_key conversion method)
^^ note 2, make sure you have "import functools" in your code

Question

In python2, for the sorted and list.sort functions, what is the difference between the key argument vs the cmp argument?

Answer

key does a comparison against some derivitive of the list values being compared (e.g. len, for length) whereas cmp uses a custom functions to compare the whole of the two list items being compared (e.g. comparing release number 1.2 and 1.2.1 via a custom function)

Question

In python, you have file called "test.txt", write code to print out all the lines from "test.txt" and use approach where you have to close the file handle explicitly.

Answer

f = open("test.txt")
for line in f:
   print line
f.close()

Question

In python, you have file called "test.txt", write code to print out all the lines from "test.txt" and use approach where you do not need to worry about closing file handles.

Answer

with open("test.txt") as f:
    for line in f:
        print line

Question

In python, if you are at the REPL (python interactive shell), and you want to know more about a method (use "sorted" method as example) like its signiture, how do you get this info?

Answer

help(sorted)

Question

In Linux, the keyboard shortcut for EOF (end of file), to exit the shell prompt for example (or exit the python REPL) is what?

Answer

ctrl-d

Question

In Linux, what is the text editor that is the most common and available by default in all distros?

Answer

vi

Question

In linux, what does the "m" in the "vim" text editor stand for?

Answer

vi "improved"

Question

In Linux, the vi text editor has two modes, [...] mode and control mode

Answer

input

Question

In Linux, the vi text editor has two modes, input mode and [...] mode

Answer

control

Question

In Linux, for the vi editor, what key do you press to exit from control mode to input mode (and viceversa)?

Answer

ESC

Question

In python, for the vi editor, when in control mode, what do you type to force quit (quit without saving)?

Answer

:q!

Question

In Linux, for the vi editor, if you are in control mode, how do you save and quit?

Answer

:wq

Question

In linux, what is the first line you use to start any shell script?

Answer

#!/bin/sh
^^ also accpetable: #!/bin/bash
^^ note there is no whitespace, and note that we are using the shebang (#!) syntax to indicate what program will be used to run the script (e.g. /bin/sh)

Question

In Linux, what does the #! syntax do when you put it at the top of any type of script/code?

Answer

It tells linux what program to use (full path) to run the script (e.g. #!/bin/sh for shell script, #!/usr/bin/python3 for python, etc)

Question

In Linux, in a shell script, how do you create a variable, x, and assign to it the value, 2?

Answer

x=2

Question

In linux, you have a shell script with line "x=2", how do you print out the value of x

Answer

echo $x
^^ note the $ syntax does parameter/variable expansion, i.e. accesses the value of x, without it just "x" gets printed

Question

In Linux, in shell scripts, the $[] syntax is called [...] [...]

Answer

expression expansion
^^ e.g. is: echo $[2*6], which would print "12" to the screen

Question

In Linux, you have shell script, that has already defined x=2 and y=3, how do you print out the sum of x and y?

Answer

echo $[x+y]

Question

In Linux, in shell scripting, the $ syntax is called [...] [...]

Answer

variable expansion

Question

In linux, in shell scripting, the $() syntax (e.g. $(pwd) ), is called [...] [...]

Answer

command expansion

Question

In Linux, in shell scripting, how do you print out the value of the pwd command (e.g. /home/kevin would be printed if you are in home directory)?

Answer

echo $(pwd)