# ---------------------
​
​
1) Get users who attended some activity more than twice.
​
"""
SELECT * FROM users;
​
user_id  username
1        John Doe
2        Jane Don
3        Alice Jones
4        Lisa Romero
​
SELECT * FROM training_details;
​
user_training_id  user_id  training_id  training_date
1                 1        1            "2015-08-02"
2                 2        1            "2015-08-03"
3                 3        2            "2015-08-02"
4                 4        2            "2015-08-04"
5                 2        2            "2015-08-03"
6                 1        1            "2015-08-02"
7                 3        2            "2015-08-04"
8                 4        3            "2015-08-03"
9                 1        4            "2015-08-03"
10                3        1            "2015-08-02"
11                4        2            "2015-08-04"
12                3        2            "2015-08-02"
13                1        1            "2015-08-02"
14                4        3            "2015-08-03"
"""
--------------------
​
"""

SELECT user_id, COUNT(training_id) AS amount
FROM training_details JOIN user
ON user.user_id = training_details.user_id
GROUP BY 1
HAVING COUNT(training_id) > 2

​
2) Implement a group_by_owners that:
Accepts a dictionary containing the file owner name for each file name.
Returns a dictionary containing a list of file names for each owner name, in any order.
For example, dictionary:
{
    'Input.txt': 'Randy',
    'Code.py': 'Stan',
    'Output.txt': 'Randy'
}
​
the group_by_owners function should return:
{
    'Randy': ['Input.txt', 'Output.txt'],
    'Stan': ['Code.py']
}
"""

def group_by_owners(file_owners):
    result = defaultdict(list)
    for key, value in file_owners.items():
        result[value].append(key)

​
#----------------------
"""
3) Sort list of objects by age field in ascending order
"""
​
"""
Input:
"""
​
animals = [
    {'type': 'penguin', 'name': 'Stephanie', 'age': 8},
    {'type': 'elephant', 'name': 'Devon', 'age': 3},
    {'type': 'puma', 'name': 'Moe', 'age': 5},
]
​

sorted_animals = sorted(animals, lambda animal: animal['age'])

"""
Output:
"""
​
sorted_animals = [
    {'type': 'elephant', 'name': 'Devon', 'age': 3},
    {'type': 'puma', 'name': 'Moe', 'age': 5},
    {'type': 'penguin', 'name': 'Stephanie', 'age': 8}
]
----------------------
​
​
​
4) What will be the output of the following code snippet?
"""
class Person:
    def __init__(self, id):
        self.id = id
​
sam = Person(100)
sam.__dict__['age'] = 49
print(sam.age + len(sam.__dict__))
---------------------
​
"""
​
5) What will be the output of the following code snippet?
"""
​
class A:
    def __init__(self):
        self.calcI(30)
        print("i from A is", self.i)
        
    def calcI(self, i):
        self.i = 2 * i
        
class B(A):
    def __init__(self):
        super().__init__()
        
    def calcI(self, i):
        self.i = 3 * i
​
b = B()
---------------
6) Write a code snippet that returns all pairs of numbers that return sum of 10
[5, 0, -1, 9, 9, 1, 3, 6, 7, 1]

def get_pairs(l):
    result = []
    for i, el in enumrate(l):
        for el_2 in l[i+1:]:
            if el + el_2 == 10:
                result.append(el, el_2)