Student_database_part2_exercise.py

# Python Exercise:
# STUDENT DATABASE MANAGEMENT SYSTEM, part 2

# PART 1
# Create a student database which stores the following information:
# student name, job, current Python level (for each student)

# The user will manage the database using the following commands:
#       add (to add a student to the database, issuing a warning if the student already exists)
#       delete (to delete a student from the database, issuing a warning if the student is not in the database)
#       print (to display information about the students, comprising tot numb of students)
#       average (to return average python level of all students)
#       exit (to exit the database)

# PART 2
#       log (to obtain a log of timestamps for every action carried out on the database)
#       save (to save the database in a csv file)
#       load (to load the database from the csv file, in format name;job;pythonlevel)



student_db={}

def get_user_command():
    # this will take a user command and then call the dispatcher
    while True:
        user_input=input('Please insert your command <add>, <delete>, <print>, <average>, <log>, <save>, <load> or type <exit> to exit the database')
        user_input_split = user_input.split()
        if(user_input.find('exit')!=-1):
            return
        dispatcher(user_input_split)

def dispatcher(cmd_list_in):
    # takes a user command and then calls the corresponding function
    if cmd_list_in[0] == 'add':
        if (len(cmd_list_in))<4:
            print("ERROR: Add function must be followed by: <name>, <job>, <python level>")
        else:
            print ("calling add - it must be followed by <name> <job> <python level>") #call function
            add_user(cmd_list_in[1], cmd_list_in[2], cmd_list_in[3])
    elif cmd_list_in[0] == 'delete':
        print ("calling delete - it must be followed by <name>") # call function
        delete_user(cmd_list_in[1])
    elif cmd_list_in[0] == 'print':
        print ("calling print") # call function
        print_user(student_db)
    elif cmd_list_in[0]=='average':
        print ("calling average") # call function
        average_user(student_db)
    elif cmd_list_in[0]=='log':
        print ("calling display log") # call function
        display_log(log_list)
    elif cmd_list_in[0] == 'save':
        print("The database has been save into the csv file called student_db")  # call function
        save_studentdb_csv(student_db)
    elif cmd_list_in[0] == 'load':
        print("Loading student database from csv file")  # call function
        load_studentdb_csv(student_db)
    else:
        print ("ERROR: commands can only be <add>, <delete>, <print>, <average> or <exit>")

def add_user(name_in, job_in, python_exp_in):
    # the dictionary will have name of students as keys and tuples (job, python level) as values
    if name_in in student_db.keys():
        print('Sorry but this name already exists in the database')
    else:
        student_db[name_in] = (job_in, python_exp_in)
        print(name_in, 'has been added to the database')
        log_action1('add',name_in)
    print("Your student database now looks as follows")
    print (student_db)
    return

def delete_user(name_in):
    if name_in not in student_db.keys():
        print('Sorry, this student is not present in the database')
    else:
        del student_db[name_in]
        print(name_in, 'has been deleted from student database')
        log_action1('delete',name_in)
    print("Your student database now looks as follows")
    print(student_db)
    return


def print_user(student_db):
    # number of students in the database
    student_numb=len(student_db)
    print('The number of the students in the database is: ', student_numb)

    # mix and max python level among students
    python_exp_list = []
    for v in student_db.values():
        python_exp_list.append(int(v[1]))
    min_python_lev=min(python_exp_list)
    max_python_lev=max(python_exp_list)
    print('The lowest python level among the students is: ', min_python_lev)
    print('The greatest python level among the students is: ', max_python_lev)

    # for all students Name: Job, python level: Value
    for k in student_db.keys():
        print (k, ':', student_db[k][0], ', python level:', student_db[k][1])
    log_action2('print')


def average_user(student_db):
    # average level of python among the students
    python_exp_list = []
    for v in student_db.values():
        python_exp_list.append(int(v[1]))
    sum_pyth_exp=sum(python_exp_list)
    average_pl=sum_pyth_exp/len(python_exp_list)
    average_pl_r=round(average_pl,2)
    print('The average value of python level for all students in the db is: ', average_pl_r)
    log_action2('average')

# define log functions for time stamps and log display
import time, datetime
log_list = []

def log_action1(action,name_in):
    my_time_stamp = datetime.datetime.now().strftime('%d %m %y | %H:%M:%S')
    log_list.append((my_time_stamp,action, name_in))
    return

def log_action2(action):
    my_time_stamp = datetime.datetime.now().strftime('%d %m %y | %H:%M:%S')
    log_list.append((my_time_stamp,action))
    return

def display_log(log_list):
    print ('The log list looks as follows:', log_list)


# define functions to save student database in a csv file and to load it from there
# csv file will have in each row student_name, job, python_level

import csv

list_studentdb = []
def save_studentdb_csv(student_db):
    # The student db dictionary need to be transformed into a list of lists for csv file
    for s in student_db.keys():
        list_studentdb.append([s,student_db[s][0],student_db[s][1]])
    print('my studentdb list:', list_studentdb)
    # write to csv file
    with open('student_db.csv','w') as csvfile:
        my_csv_writer = csv.writer(csvfile)
        my_csv_writer.writerows(list_studentdb)

def load_studentdb_csv(student_db):
    fh1 = open('student_db.csv','r')
    csv_content=fh1.read()
    csv_rows=csv_content.split('\n')
    fh1.close()