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ewis:laboratoare:02 [2020/02/28 18:59] alexandru.predescu |
ewis:laboratoare:02 [2023/03/15 17:40] (current) alexandru.predescu [Data Structures] |
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| ===== Lab 2 - Data Structures. Functions. Modules ===== | ===== Lab 2 - Data Structures. Functions. Modules ===== | ||
| - | ===== Laboratorul 02. ===== | ||
| - | |||
| ==== Functions ==== | ==== Functions ==== | ||
| Line 26: | Line 24: | ||
| </code> | </code> | ||
| - | **T1 (2p)** Having a list of numbers, write a function to calculate the sum of all elements in the list. | + | **T1 (1p)** Having a list of numbers, write a function to calculate the sum of all elements in the list. |
| Tip: List given as input, using a for loop | Tip: List given as input, using a for loop | ||
| </note> | </note> | ||
| Line 34: | Line 32: | ||
| import math | import math | ||
| - | import module1 as m | ||
| - | |||
| - | m.hello_name("Alex") | ||
| - | |||
| - | my_list = [1, 2, 3, 4, 5] | ||
| - | print(my_list) | ||
| - | my_list.append(6) | ||
| - | print(my_list) | ||
| - | my_other_list = [7, 8, 9, 10] | ||
| - | my_list.extend(my_other_list) | ||
| - | print(my_list) | ||
| - | my_list.sort(reverse=True) | ||
| - | print(my_list) | ||
| - | |||
| - | |||
| list1 = [1, 3, 4, 5, 8] | list1 = [1, 3, 4, 5, 8] | ||
| list3 = [1, 3, -4, 5, -8, -12] | list3 = [1, 3, -4, 5, -8, -12] | ||
| Line 55: | Line 38: | ||
| # function to compute the arithmetic mean of a list | # function to compute the arithmetic mean of a list | ||
| - | |||
| def my_mean(v): | def my_mean(v): | ||
| - | s_elem = sum(v) | + | s_elem = sum(v) |
| n_elem = len(v) | n_elem = len(v) | ||
| - | return s_elem/n_elem | + | return s_elem / n_elem |
| # function to compute the weighted arithmetic mean of a list | # function to compute the weighted arithmetic mean of a list | ||
| - | |||
| def my_pmean(v, p): | def my_pmean(v, p): | ||
| Line 70: | Line 51: | ||
| s_lp = 0 | s_lp = 0 | ||
| while i < len(v): | while i < len(v): | ||
| - | s_lp += v[i]*p[i] | + | s_lp += v[i] * p[i] |
| i += 1 | i += 1 | ||
| - | return s_lp/s_pond | + | return s_lp / s_pond |
| # function to compute the variance and standard deviation of a list | # function to compute the variance and standard deviation of a list | ||
| - | |||
| def my_stdvar(v): | def my_stdvar(v): | ||
| Line 83: | Line 63: | ||
| for elem in v: | for elem in v: | ||
| s += (elem - m)**2 | s += (elem - m)**2 | ||
| - | return s/n, math.sqrt(s/n) | + | return s / n, math.sqrt(s / n) |
| - | + | ||
| - | # function to compute the L2-norm nornalization for list | + | |
| + | # function to compute the L2-norm normalization for list | ||
| def l2norm(v): | def l2norm(v): | ||
| new_list = [] | new_list = [] | ||
| s = 0 | s = 0 | ||
| + | # compute the L2 norm | ||
| for elem in v: | for elem in v: | ||
| s += elem**2 | s += elem**2 | ||
| s = math.sqrt(s) | s = math.sqrt(s) | ||
| + | | ||
| + | # list normalization using the L2 norm | ||
| for elem in v: | for elem in v: | ||
| - | new_elem = elem/s | + | new_elem = elem / s |
| new_list.append(new_elem) | new_list.append(new_elem) | ||
| + | | ||
| + | # TODO: same task with list comprehension | ||
| + | | ||
| return new_list | return new_list | ||
| | | ||
| </code> | </code> | ||
| - | **T2 (2p)** Use the functions to compute the arithmetic mean, weighted arithmetic mean, variance, standard deviation and L2-norm normalization of the list | + | **T2.1 (1p)** Use the functions to compute the arithmetic mean, weighted arithmetic mean, variance, standard deviation and L2-norm normalization of the list |
| + | |||
| + | **T2.2 (2p)** Implement the functions using list comprehension, without using for loops | ||
| </note> | </note> | ||
| Line 111: | Line 98: | ||
| <note> | <note> | ||
| - | //module1.py// | + | **//module1.py//** |
| <code python> | <code python> | ||
| def hello_name(name): | def hello_name(name): | ||
| print("Hello " + name) | print("Hello " + name) | ||
| - | return | ||
| </code> | </code> | ||
| - | //main.py// | + | **//main.py//** |
| <code python> | <code python> | ||
| Line 125: | Line 111: | ||
| from module1 import hello_name | from module1 import hello_name | ||
| hello_name("Alex") | hello_name("Alex") | ||
| + | |||
| # import all resources from a module | # import all resources from a module | ||
| from module1 import * | from module1 import * | ||
| hello_name("Alex") | hello_name("Alex") | ||
| + | |||
| # import the module | # import the module | ||
| import module1 | import module1 | ||
| module1.hello_name("Alex") | module1.hello_name("Alex") | ||
| + | |||
| # import the module using an alias | # import the module using an alias | ||
| import module1 as m | import module1 as m | ||
| Line 136: | Line 125: | ||
| </code> | </code> | ||
| - | **T3 (2p)** Create two Python files (.py) as in the example. Run the program //main.py// and check the output in the console | + | **T3 (2p)** Create two Python files (.py) in the same project folder, as shown in the example. Run the program //main.py// and check the output in the console |
| </note> | </note> | ||
| Line 146: | Line 135: | ||
| === Lists === | === Lists === | ||
| - | List is one of the most frequently used and very versatile datatype used in Python. As opposed to more traditional arrays, used to store elements having the same data-type, Python lists do not have such constrain. Lists are discussed in the previous lab ([[ewis:laboratoare:01|]]), showing how to create, read, update and delete (CRUD) contained elements using basic operators. In Python, the List type also contains some useful methods: append, extend, insert, remove, pop, clear, index, count, sort, reverse, copy | + | List is one of the most frequently used and very versatile datatype used in Python. As opposed to more traditional arrays, used to store elements having the same data-type, Python lists do not have such constrain. Lists are discussed in the previous lab ([[ewis:laboratoare:01|]]), showing how to create, read, update and delete (CRUD) contained elements using basic operators. In Python, the List type also contains some useful methods: append, extend, insert, remove, pop, clear, index, count, sort, reverse, copy. |
| <note> | <note> | ||
| Line 152: | Line 141: | ||
| my_list = [1, 2, 3, 4, 5] | my_list = [1, 2, 3, 4, 5] | ||
| print(my_list) | print(my_list) | ||
| + | |||
| # add an element to the list | # add an element to the list | ||
| my_list.append(6) | my_list.append(6) | ||
| print(my_list) | print(my_list) | ||
| + | |||
| # combine lists | # combine lists | ||
| my_other_list = [7, 8, 9, 10] | my_other_list = [7, 8, 9, 10] | ||
| my_list.extend(my_other_list) | my_list.extend(my_other_list) | ||
| print(my_list) | print(my_list) | ||
| + | |||
| # sort list (descending) | # sort list (descending) | ||
| my_list.sort(reverse=True) | my_list.sort(reverse=True) | ||
| print(my_list) | print(my_list) | ||
| + | |||
| + | # check if an element is found in the list | ||
| + | # (python specific, normally used with sets or dictionaries) | ||
| + | print(1 in my_list) | ||
| + | print(10 in my_list) | ||
| </code> | </code> | ||
| </note> | </note> | ||
| Line 171: | Line 168: | ||
| <note> | <note> | ||
| - | Create, access, check membership | + | **Create, access, check membership** |
| <code python> | <code python> | ||
| Line 186: | Line 183: | ||
| </code> | </code> | ||
| - | Modify | + | **Modify** |
| <code python> | <code python> | ||
| Line 210: | Line 207: | ||
| </code> | </code> | ||
| - | Operations (set theory) | + | **Operations (set theory)** |
| <code python> | <code python> | ||
| Line 246: | Line 243: | ||
| **T4 (4p)** The set is a collection of unordered (and unique) elements. Use this to your advantage to remove duplicates from a list | **T4 (4p)** The set is a collection of unordered (and unique) elements. Use this to your advantage to remove duplicates from a list | ||
| - | Tip: | + | Hint: |
| - | *you can create a set from a list | + | *you can create a set from a list: ''s = set([1,2,3])'' |
| - | *you can create a list from a set | + | *you can create a list from a set: ''v = list({1, 2, 3})'' |
| </note> | </note> | ||
| Line 281: | Line 278: | ||
| # looping through a dictionary: | # looping through a dictionary: | ||
| for key in d: | for key in d: | ||
| - | print(key) # print only key | + | print(key) # print only key |
| - | print(key, d[key]) # print key and value d[key] | + | print(key, d[key]) # print key and value d[key] |
| Line 300: | Line 297: | ||
| else: | else: | ||
| print('not found') | print('not found') | ||
| + | |||
| + | </code> | ||
| + | |||
| + | <code python> | ||
| # counting the number of times a letter appears in a string: | # counting the number of times a letter appears in a string: | ||
| Line 319: | Line 320: | ||
| Apriori algorithm, a classic algorithm, is useful in mining frequent itemsets and relevant association rules. Usually, you operate this algorithm on a database containing a large number of transactions. | Apriori algorithm, a classic algorithm, is useful in mining frequent itemsets and relevant association rules. Usually, you operate this algorithm on a database containing a large number of transactions. | ||
| </note> | </note> | ||
| + | |||
| + | <note> | ||
| + | |||
| + | **T5 (4p - bonus)** You have a list of numbers. Write a program to show the frequency of each number as the number of times that number is found in the list. | ||
| + | |||
| + | Hint: | ||
| + | * Use dictionaries to keep track of each element | ||
| + | </note> | ||
| + | |||
| + | **Resources**: | ||
| + | |||
| + | * [[http://mathworld.wolfram.com/L2-Norm.html|L^2-Norm]] | ||
| + | * [[http://mathworld.wolfram.com/StandardDeviation.html|Standard Deviation]] | ||
| + | * [[https://www.youtube.com/watch?v=WGlMlS_Yydk|Apriori Algorithm (Associated Learning) - Fun and Easy Machine Learning]] | ||
| + | |||
| + | |||
