Lecture "Brute-force algorithms", exercise 3

[essepuntato]

Write in Python the function def my_enumerate(input_list) which behave like the built-in function enumerate() introduced in Section "Linear search" and returns a proper list, and accompany the function with the related test case. It is not possible to use the built-in function enumerate() in the implementation.

[delfimpandiani]

If I understood the prompt correctly, the point of the exercise is to create a new function called my_enumerate(), which should behave just like the built-in function enumerate()

def my_enumerate(input_list):
    result = list() # new empty list where to store the resulting list
    position = 0 # initialize position to the first one, 0
    for item in input_list: # for each item in the original input_list
        new_item = position, item
        result.append(new_item) # apend the item and its position to the new list
        position += 1 # increase the position by one
    return result

# accompany the function with the related test case

# Test case for the algorithm
def test_my_enumerate(input_list, expected):
    result = my_enumerate(input_list)
    if expected == result:
        return True
    else:
        return False

# Three different test runs
print(test_my_enumerate([15, 38, 56, 4], [(0, 15), (1, 38), (2, 56), (3, 4)]))
print(test_my_enumerate(["A", "B", "C", "D"], [(0, 'A'), (1, 'B'), (2, 'C'), (3, 'D')]))
print(test_my_enumerate(["A", 78, "Hola", 6], [(0, 'A'), (1, 78), (2, 'Hola'), (3, 6)]))

[EleonoraPeruch]

[federicabologna]

I tried to use len() as in the Insertion sort algorithm, and for once it worked! YEY!

def test_my_enumerate(input_list, expected):
    result = my_enumerate(input_list)
    if expected == result:
        return True
    else:
        return False

def my_enumerate(input_list):
    result = list()
    for item in input_list:
        position = len(result)
        new_item = item, position
        result.append(new_item)
    return result

print(test_my_enumerate((["a", "b", "c"]), [('a', 0), ('b', 1), ('c', 2)]))
print(test_my_enumerate((["a", "b", "c"]), [('a', 3), ('b', 1), ('c', 2)]))

[MattiaSpadoni]

[friendlynihilist]

Thanks to @delfimpandiani for the patience and the help (you're a very good teacher):

def test_my_enumerate(input_list, expected):
    result = my_enumerate(input_list)
    if expected == result:
        return True
    else:
        return False

def my_enumerate(input_list):
    res_list = list()
    n = 0

    for item in input_list:
        new_item = n, item
        res_list.append(new_item)
        n += 1
    return res_list

input_list = ["a", "b", "c", "d"]
print(my_enumerate(input_list))

print(test_my_enumerate(["a", "b", "c", "d"], [(0, "a"), (1, "b"), (2, "c"), (3, "d")])) #true
print(test_my_enumerate(["a", "b", "c", "d"], [(0, "a"), (2, "b"), (1, "c"), (3, "d")])) #false
print(test_my_enumerate(["a", "b", "c", "d"], [(0, "a"), (1, "c"), (2, "b"), (3, "d")])) #false

[lisasiurina]

Thank you @delfimpandiani and @federicafaithbologna hugs and kisses :)

def test_my_enumerate(input_list, expected):
    result = my_enumerate(input_list)
    if expected == result:
        return True
    else:
        return False

def my_enumerate(input_list):
    result = list()
    for item in input_list:
        position = len(result)
        new_item = item, position
        result.append(new_item)
    return result

print(test_my_enumerate((['Miami', 'Heat', '23']), [('Miami', 0), ('Heat', 1), ('23', 2)]))

[SeverinJB]

# Testing Algorithm
def test_my_enumerate(input_list, expected): 
    result = my_enumerate(input_list) 
    if expected == result: 
        return True 
    else: 
        return False

# Algorithm
def my_enumerate(input_list): 
    enumerate_object = []
    for item in input_list: 
        position = input_list.index(item)
        tmp_tuple = (position, item)
        enumerate_object.append(tmp_tuple)
    return enumerate_object

# Testing Input
print(test_my_enumerate(["the","ultimate","question"], [(0,"the"),(1,"ultimate"),(2,"question")]))

[ilsamoano]

I had to look at my colleagues examples, but in the end I've understood the logic behind the following example

def test_my_enumerate(oldlist,expected):
    result = my_enumerate(oldlist)

    if result == expected:
        return True
    else:
        return False

def my_enumerate(oldlist):
    newlist = list()
    position = 0

    for item in oldlist:
       new_list_item = position, item
       newlist.append(new_list_item)
       position += 1

    return newlist

print(test_my_enumerate(["Ron","Hermione","Draco"],[(0,"Ron"),(1,"Hermione"),(2,"Draco")]))  

[mangiafrangette]

def test_my_enumerate(input_list, expected):
    return my_enumerate(input_list) == expected

def my_enumerate(input_list):
    enumerate_list = list()

    for i in range(len(input_list)):
        enumerate_list.append(i)
        enumerate_list.append(input_list[i])

    return enumerate_list

list1 = ["Vettel", "Hamilton", "Bottas"]
list2 = ["Rossi", "Marquez", "Dovizioso"]
list3 = ["Peroni", "Italia", "Tamburini"]

expected1 = [0, "Vettel", 1, "Hamilton", 2, "Bottas"]
expected2 = [0, "Rossi", 1, "Marquez", 2, "Dovizioso"]
expected3 = [0, "Peroni", 1, "Italia", 2, "Tamburini"]

print(test_my_enumerate(list1, expected1))
print(test_my_enumerate(list2, expected2))
print(test_my_enumerate(list3, expected3))

@essepuntato shouldn't we put the built in function enumerate() as expected result?

[tceron]

[simayguzel]

def test_my_enumerate(input_list, expected):
    result = my_enumerate(input_list)

    if result == expected:
        return True
    else:
        return False

def my_enumerate(input_list):

    result = []
    position = 0

    for item in input_list:
        new_list = position, item
        result.append(new_list)
        position += 1

    return result

print(test_my_enumerate(["T", "R", "S", "U"], [(0, "T"), (1, "R"), (2, "S"), (3, "U")])) 
print(test_my_enumerate(["Bologna", "Roma", "Napoli", "Sicilia"], [(0, "Bologna"), (3, "Roma"), (2, "Napoli"), (1, "Sicilia")])) 
print(test_my_enumerate(["pizza", "pasta", "cannoli", "lasagna"], [(0, "pizza"), (1, "cannoli"), (2, "lasagna"), (3, "pasta")])) 

True
False
False

[andreamust]

def test_my_enumerate(input_list: object, expected: object):
    result = my_enumerate(input_list)
    if result == expected:
        return True
    else:
        return False

def my_enumerate(input_list):
    results = list()
    position = 0
    for item in input_list:
        new_item = position, item
        results.append(new_item)
        position += 1
    return results

print(test_my_enumerate(["red", "blue", "yellow", "pink"], [(0, "red"), (1, "blue"), (2, "yellow"), (3, "pink")]))   #output: True
print(test_my_enumerate(["A", "B", "C", "D"], [(1, 'A'), (1, 'B'), (2, 'C'), (3, 'D')]))   #output: False

[essepuntato]

Hi all,

here my take on the exercise (available also as Python file in the GitHub repository), with some comments:

# Test case for the algorithm
def test_my_enumerate(input_list, expected):
    result = my_enumerate(input_list)
    if expected == result:
        return True
    else:
        return False

# Code of the algorithm
def my_enumerate(input_list):
    l = list()
    for i in range(len(input_list)):
        l.append((i, input_list[i]))
    return l

print(test_my_enumerate([], []))
print(test_my_enumerate(["a", "b", "c"], [(0, "a"), (1, "b"), (2, "c")]))

Some comments:

1. @mangiafrangette I would suggest not to use enumerate in the test, since actually that function does not return a proper list (i.e. what I've asked you to return) but rather an enumeration – which is similar to list but it is not.

2. test-driven development: all the tests must be passed in order to claim that an algorithm returns what it is expected. If a test execution return False, the test is not passed. If you need to check the non-compliancy of the execution of a function on purpose, then you have to create an additional testing function that returns True if the condition of the test is not passed. Remeber: first write the test, then develop the algorithm/function.

3. Python code and indentation: please, in your answers to the various questions, if you have to write down a Python code, be sure that the correct indent is preserved by previewing your post before to publish it. You can use the ``` environment for defining your Python code, e.g.:

```
write your Python code here
```