In this lab, we$$re organizing data into different structures so we can ask and answer different questions about it$.$ Often, when we read data in from a CSV file, we start with a $2$D list that mirrors the file. So we$$ll start with that today, and reorganize the data a few different ways.

We have $$might come in handy...$$ hints for each problem. You can feel free to ignore these, they are just there as potentially helpful hints depending on how you approach the problem. We$$ve put them first under each problem, but you might want to come back to these hints after you$$ve read the rest of the problem and maybe started your solution.

Problem $1(2$D List to Dictionary$)$

Might come in handy...

Handout: Python Dictionaries

List slicing. Use lst$[1$:$]$ to get everything except position $0$ in the list lst$.$

Write a function that, given a $2$D list, creates and returns a dictionary that has one key$/$value pair for each sublist. The key is the first element from the sublist $($as a single element$),$ and the value is the rest of the sublist $($as a list$).$

You can assume that the first element in each row is distinct, so you don$$t need to worry about overwriting keys. Here are the specs:

Function name: lst$\_$to$\_$dct

Parameters: a $2$D list of any data type, of the form $[[$x$,$ y$,$ z$],[$x$,$ y$,$ z$]...]$

Returns: a dictionary where the key $=$ x and value $=[$y$,$ z$]$ for every row in the $2$D list

Examples of calling your function:

lst$\_$to$\_$dct$([[1,2,3],[4,5,6]]).....$ returns $\{1$ : $[2,3],4$ : $[5,6]\}$

lst$\_$to$\_$dct$([[10,11],[12,13]]).....$ returns $\{10$ : $[11],12$ : $[13]\}$

Problem $2($Column to List$)$

Might come in handy...

Handout: Lists and Loops

Write a function that, given a $2$D list and a column number, returns all the values from that column as a list. You can assume that a valid column number was given to your function.

Function name: col$\_$to$\_$lst

Parameters: a $2$D list of any data type, integer for a column number

Returns: a list of the same data type, containing all values from one column

Examples of calling your function:

col$\_$to$\_$lst$([[1,2],[3,4]],0)....$returns $[1,3]$

col$\_$to$\_$lst$([[1,2],[3,4],[5,6]],1)....$returns $[2,4,6]$

Problem $3($List of Sums$)$

Might come in handy...

List comprehension. This is a quick way to make a new list with $10$x the value from an original lst$....$ newlst $=[$num $*10$ for num in lst$]$

Remember that it$$s totally fine to write small helper functions, or to call functions you$$ve already written.

Write a function that takes in a $2$d list. You can assume every element in the list is a number. Your function should create and return a list of numbers that represents the sum of each column.

Here are the specs:

Function name: sum$\_$cols

Parameters: a $2$d list of numbers

Returns: a list of numbers, the sum of each column

Examples of calling your function:

sum$\_$cols$([[10,20],[1,1]]).....$ returns $[11,21]$

sum$\_$cols$([[1,2,3],[4,5,6]]).....$ returns $[5,7,9]$

Problem $4($Max in a Dictionary of Lists$)$

Might come in handy...

Python has a built$-$in max function that can accept a list. However if you give max a dictionary, it will find the maximum key, not maximum value.

You can use list$($dct$.$keys$())$ or list$($dct$.$values$())$ to turn the keys or values of a dictionary into an actual list data type

Pythons lst$.$index$($value$)$ method returns the position of the first occurrence of value in the list lst$.$

Write a function that takes in a dictionary like you would have produced in Problem $1.$ This dictionary has all of its values as lists, and we want to find the largest element at a given position among all of them. For example, if the given position is $1,$ then look at all the position $1$s in all of the lists, and return the key where the element at position $1$ is the largest.

Here are the specs:

Function name: find$\_$max

Parameters: a dictionary where every value is a list, and an integer for a position

Returns: the key in the given dictionary, where its value at a given position is the highest

Examples of calling your function:

find$\_$max$(\{"$a$"$ : $[1,5],"$b$"$ : $[4,3]\},0).....$ returns $"$b$"$

find$\_$max$(\{"$a$"$ : $[1,5],"$b$"$ : $[4,3]\},1).....$ returns $"$a$"$

Problem $5(2$D List to List of Dictionaries$)$

Might come in handy...

In this case the header will be at lst$[0],$ and the main data will be at lst$[1$:$]$

Because we$$re making a list of dictionaries, you should make a new list $($newlst $=[])$ at least once, and a new dictionary $($dct $=\{\})$ many times.

Write a function that, given a $2$D list which includes a header, creates and returns a list dictionaries. All the dictionaries have the same keys, which come from the header.

Imagine a $2$d list representing a CSV file with a header, like this:

name

attribute

fault

Grizz

happy

barking

Carol

hugs

jealous

We want it to turn into a list of two dictionaries, each with three key$/$value pairs, like this:

$[\{"$name$"$ : "Grizz",

"attribute" : "happy",

"fault" : "barking"$\},$

$\{"$name$"$ : "Carol",

"attribute" : "hugs",

"fault" : "jealous"$\}]$

You can assume the given list is not empty, and that ever