on 09-Oct-2018 (Tue)

Question

In linux, to move/copy a file/dir, what two flags should you always include to keep the file permissions/symlinks, etc intact (use the flags on cp for the answer)?

Answer

cp -pd
^^ p is to preserve mode, ownership, timestamps, and d is to preserve links (no de-reference)

Question

In linux, aside from the man command, the [...] command also contain some excellent reference and tutorial information in hypertext linked format, but not all commands are covered.

Answer

info

Question

In linux, [...] is the command to activate the calculator program.

Answer

bc

Question

In Linux, issue command to find out how much disk space is being used by the user home directory?

Answer

du -sh ~
^^ the -s is for summary and just gives total disk usage of home dir and all its subdirs, without listing each sub dir one by one

Question

In linux, the [...] command will tell you the type of a file based on the first few bytes of its content (aka its magic numbers).

Answer

file

Question

In Linux, you have a file called, test.txt, how do you output the first 20 lines of this file?

Answer

head -n 20 test.txt

Question

In Linux, you have lots of lines created by output of "ls -l /bin/", so type command to best view the output page by page?

Answer

ls -l /bin/ | less

Question

In Linux, [...] is the GNU version of more, but with extra features (like arrow up and down usage, etc).

Answer

less

Question

In python, if you want to count the occurrences of like items in a sequence; for example count the occurrences of words in a body of text, it is best to use what data structure?

Answer

dictionary

Question

In python, if you have a dictionary, called count, which has each word in a book as its key, and the number of occurances of that word as its value, how do you create a second dictionary, count2, which is just the dictionary of words that appear between 15 and 20 times in the book (use dictionary comprehension)?

Answer

count2 = { key:value for key, value in count.items() if value <= 20 and value >= 15 }

Question

In python, [...] are unordered collections of unique items

Answer

sets

Question

In python, there are two types of sets, immutable and mutable, the immutable set is called [...]

Answer

frozenset

Question

In python, how do you create an empty mutable set, s?

Answer

s = set()
^^ note s = {}, whould NOT work as it would create an empty dictionary

Question

In python, you have set, s, returns the number of elements in s.

Answer

len(s)

Question

In python, you have set, s={1,2,3}, how do you create a second set, s2, that is copy of s but you can change independently of s?

Answer

s2 = s.copy()

Question

In python, you have sets, s={1,2,3} and t={3,4,5}, return a set, u, of all items in s but not in t (i.e. {1,2} )

Answer

u = s.difference(t)

Question

In python, you have sets, s={1,2,3}, t={3,4,5}, return a set, u, of all items in both t and s (so u has value {3} )

Answer

u = s.intersection(t)

Question

In python, you have two sets, s and t, check if s and t have no items in common.

Answer

s.isdisjoint(t)
^^ returns True

Question

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

Answer

s.issubset(t)

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 python, you have sets, s={1,2,3}, t={3,4,5}, return a set, u, of all items in s or t (i.e. {1,2,3,4,5})

Answer

u = s.union(t)

Question

In python, you have sets, s={1,2,3} and t={3,4,5}, returns a set, u, of all items that are in s or t, but not both (i.e. {1,2,4,5} ).

Answer

u = s.symmetric_difference(t)

Question

In python, you have set, s = {1,2,3}, add item 'a' to s (so s ends up as {1,2,3,'a'} ).

Answer

s.add('a')

Question

In python, you have sets, s= {1,2,3} and t={3,4,5}, remove all items in s that are also in t (i.e. s ends up as {1,2} ).

Answer

s.differenece_update(t)

Question

In python, you have sets, s={1,2,3,4} and t={3,4,5}, remove all items from s that are not in the intersection of s and t (i.e. s ends up as {3, 4} )

Answer

s.intersection_update(t)

Question

In python, you have set, s = {1,2,3}, remove 3 from s (so s ends up as {1,2} ).

Answer

s.remove(3)

Question

In python, you have sets, s={1,2,3} and t={3,4,5}, call method on s so s ends up as {1,2,4,5}

Answer

s.symmetric_difference_update(t)

Question

In python, you have sets, s = {1,2,3,4} and t = {3,4,5}, what is the value of s after you do s.symmetric_difference_update(t)?

Answer

{1,2,5}

Question

In python, you have set, s = {1,2,3}, how do you adds all the items of list, l=[4,5,6] to s (so s ends up as {1,2,3,4,5,6} )?

Answer

s.update(l)

Question

In python, the set object (for example s={1,2,'a',(1,2)} ) does not care that its members are not all of the same type as long as they are all [...]

Answer

immutable

Question

In python, [...] types all have a hash value that does not change throughout the lifetime of the instance

Answer

hashable

Question

In python, all built-in immutable types are [...] while all mutable types are not.

Answer

hashable

Question

In python, frozenset is useful in place of a set in 2 cases, when you want to add a set to another set (since frozenset is immutable) and [...]

Answer

when you want to make a set the key to a dictionary

Question

In python, frozenset is useful in place of a set in 2 cases, when you want to make a set a key to a dictionary (since its immutable) and [...]

Answer

when you want to add a set to another set