Lecture 6 bis : Additional exercices

December, 2021 - François HU

Master of Science - EPITA

This lecture is available here: https://curiousml.github.io/

Exercices

These exercices are considered "normal-hard" exercices.

Exercice 1: lists

Create a function insert, that produces the following results:

>>> l = [0, 9, 3, 10]
>>> print(insert(l, -1, 1))
[0, -1, 9, 3, 10]
>>> print(insert(l, -1, 2))
[0, 9, -1, 3, 10]
>>> print(insert(l, "epita", 4))
[0, 9, 3, 10, 'epita']
>>> print(insert(l, "epita", 10))
[0, 9, 3, 10, 'epita']
>>> print(l)
[0, 9, 3, 10]

Exercice 2: dictionaries

we have the following list of dictionaries

paris = [{"District": 3, "Date":2007, "Pop":34576},
         {"District": 5, "Date":2007, "Pop":62664},
         {"District": 6, "Date":2007, "Pop":45332},
         {"District": 7, "Date":2007, "Pop":57410},
         {"District": 8, "Date":2007, "Pop":39165},
         {"District": 9, "Date":2007, "Pop":58632},
         {"District": 10, "Date":2007, "Pop":93373},
         {"District": 11, "Date":2007, "Pop":151421},
         {"District": 12, "Date":2007, "Pop":142425},
         {"District": 13, "Date":2007, "Pop":179213},
         {"District": 14, "Date":2007, "Pop":134382},
         {"District": 15, "Date":2007, "Pop":232247},
         {"District": 16, "Date":2007, "Pop":159706},
         {"District": 17, "Date":2007, "Pop":164673},
         {"District": 18, "Date":2007, "Pop":191523},
         {"District": 19, "Date":2007, "Pop":184038},
         {"District": 20, "Date":2007, "Pop":194018}]

• write a script that add a field Rounded_pop which discard the last 3 digits. For example we transform the value 34576 to 34

• write a script that store the values of Rounded_pop into a list named populations

• sort by ascending order the list populations

Exercice 3: strings

we have the following list of strings

list_of_strings = [
    'EPITA', 'propose', 'trois', 'programmes',
    'spécialisés', 'Master', 'of', 'Science', 
    'dans', 'un', 'environnement', 'international.',
    'Cette', 'formation', 'professionnalisante', 'de',
    '18', 'mois', 'intégralement', 'en', 'anglais',
    'pour','les','étudiants','français', 'et', 'internationaux,', 
    'permet', 'de', 'se', 'spécialiser', 'dans', 'un', 
    'domaine', 'après', '3', 'ou', '4', 'ans', 'd’études.']

Write a script that create a variable named text which concatenante the items of list_of_strings with exactly one space between words.

Exercice 4: arrays

• Generate the following array without explicit loops and without manually fill in the numbers. We will name it arr1:

[[  0  25 100 225 400]
 [  1  36 121 256 441]
 [  4  49 144 289 484]
 [  9  64 169 324 529]
 [ 16  81 196 361 576]]

• Extract the diagonal values of arr1 (do not generate it) and call it diag1

[  0,  36, 144, 324, 576]

• From arr1, extract the submatrix:

[[225 100  25]
 [289 144  49]
 [256 121  36]]

and name it subarr1.

Exercice 5: arrays

• Generate the following array without explicit loops and without manually fill in the numbers. We will name it arr2:

[[10  9  8  7  6]
 [ 9  8  7  6  5]
 [ 8  7  6  5  4]
 [ 7  6  5  4  3]
 [ 6  5  4  3  2]]

• Replace all the even values of arr2 by 0 without explicit loops. You should have:

  [[0 9 0 7 0]
  [9 0 7 0 5]
  [0 7 0 5 0]
  [7 0 5 0 3]
  [0 5 0 3 0]]

Exercice 6: plotting

• Generate and (scatter) plot 2000 random points in the space $[−10,0]×[1,2]$ with the color orange. You should have:

• color the points inside the space $[−4,-2]×[1.2,1.8]$ or $[−8,-6]×[1.2,1.8]$ by green. You should have:

Exercice 7: data manipulation

• Import the Iris and defra_consumptiondatasets as dataframes and name them respectively iris and cons. You should have the following first 5 rows for each dataframe:

• For the dataframe iris (aside from the column species):
  • discard the Cm at the end of each column name
  • convert values to minimeter (instead of centimiter)

• For the dataframe cons, convert columns to percentages of the totals. Therefore the first row should be: