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Khaled Said
Khaled Said

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Advanced usage of map & filter in Python

In 2 different job interviews I got asked to solve the following question using python. so I thought it would be good to publish the solution for the question.

You have the following relation:

    AttendanceActions ||--o{ Attendance : AttendanceId
    AttendanceActions {
        int id
        int AttendanceId
        datetime ActionTime
        text Action
    Attendance {
        int id
        date day
        text employee
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and the following tables:


id day employee
1 2020-04-01 EMP01
2 2020-04-01 EMP02
3 2020-04-02 EMP01
4 2020-04-03 EMP01
5 2020-04-02 EMP02
6 2020-04-03 EMP02


id AttendanceId ActionTime Action
1 1 2020-04-01 12:00 AM CheckIn
2 1 2020-04-01 12:00 PM CheckOut
3 2 2020-04-01 12:05 PM CheckIn
4 2 2020-04-01 11:50 PM CheckOut
5 3 2020-04-02 12:05 AM CheckIn
6 3 2020-04-02 11:50 AM CheckOut
7 3 2020-04-02 11:50 PM CheckIn
8 4 2020-04-03 12:05 PM CheckOut


You are given a simple SQLITE3 database for an attendance system with a small set of data.
An employee can perform one of two actions: CheckIn or CheckOut. When an action is performed, it is stored at 2 levels:

  • An attendance entry is created for the day if no actions were previously performed on that day
  • An attendance action entry is created recording the time for this specific action and linked to the day’s attendance record

For example, if EMP01 checks in at midnight of 2020-04-01, two records are created:

  • A record in the Attendance table with date 2020-04-01 and employee EMP01
  • A record in the AttendanceActions table referencing the previous attendance record with time 2020-04-01 12:00 AM

The time stamps are stored in local server time, which is in the Cairo timezone (UTC + 2). This is not a good practice, but it’s based on a real-world case.


01 Check day attendance for employee

Write a function that accepts an employee code (e.g. EMP01) and a date (e.g. 2020-04-01) and reports whether the employee has attended that day and how long.

get_attendance('emp01', '2020-04-01')
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on the sample data should return the following dictionary:

    "attended": True,
    "duration": "12:00"
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The employee attended from 12:00 AM to 12:00 PM, which is exactly 12 hours.
For 2020-04-02, the employee attended from 12:05 AM to 11:50 AM (11:45 night shift), then checked in again for his next shift at 11:50 PM (so 10 minutes before midnight the next day) for a total of 11:55:

    "attended": True,
    "duration": "11:55"
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For 2020-04-03, the employee checked out at 12:05 PM for a duration of 12:05 (12 hours 5 minutes) calculated from midnight since his last check-in was the previous day.


from datetime import datetime, timedelta
import sqlite3

def _convert_string_datetime(time):
    return datetime.strptime(time, '%Y-%m-%d %I:%M %p')

def get_attendance(employee: str, tdate: str):
    emp = employee
    start_time = datetime.strptime(tdate, '%Y-%m-%d') - timedelta(minutes=15)
    end_time = (start_time + timedelta(days=1, minutes=15))
    query = '''
    SELECT *, et.ActionTime forwardTime FROM
            (LEAD  (, 1,0) OVER (ORDER BY forwardID 
        FROM AttendanceActions ac
        INNER JOIN Attendance a ON ac.Attendanceid =
        WHERE a.employee = '{}' ORDER BY ee 
    LEFT JOIN AttendanceActions et ON ee.forwardID =
    with sqlite3.connect('attendance.db') as con:
        cur = con.cursor()
        db_res = cur.execute(query)
        p_res = db_res.fetchall()
        pt_res = list(map(lambda x: x[1] - x[0], filter(
            lambda x: start_time < x[0] < end_time and x[2] == 'CheckIn', map(
                lambda x: ((_convert_string_datetime(x[1]) if x[1] else 0),
                           (_convert_string_datetime(x[8]) if x[8] else 0), x[2]), p_res))))
        if not pt_res:
            return {
                "attended": False,
                "duration": "00:00"
            return {
                "attended": True,
                "duration": str(pt_res[0])

print(get_attendance('EMP01', '2020-04-01'))
print(get_attendance('EMP01', '2020-04-02'))
print(get_attendance('EMP01', '2020-04-03'))
print(get_attendance('EMP02', '2020-04-01'))
print(get_attendance('EMP02', '2020-04-02'))
print(get_attendance('EMP02', '2020-04-03'))
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