Assignment07.py

#------------------------------------------#
# Title: Assignment07.py
# Desc: Working with files and exception.
# Change Log: (Who, When, What)
# DBiesinger, 2030-Jan-01, Created File
# AnhVu, 2021-Aug-12, Added Code 
# AnhVu, 2021-Aug-22, Added Code for Error Handling
#------------------------------------------#

# -- DATA -- #
strChoice = '' # User input
lstTbl = []  # list of lists to hold data
dicRow = {}  # list of data row
strFileName = 'CDInventory.txt'  # data storage file
objFile = None  # file object


# -- PROCESSING -- #
class DataProcessor:    
    # TODone add functions for processing here
    @staticmethod
    def additem (strID, strTitle, stArtist):
        """Function to add new data to the table
     
         Args:
             strID: ID number for the new record
             strTitle: Title of the new record
             stArtist: Artist name of the new record 
     
         Returns:
             None.
        """
       # TODone move processing code into function
        intID = int(strID)
        dicRow = {'ID': intID, 'Title': strTitle, 'Artist': stArtist}
        lstTbl.append(dicRow)
        
    
    @staticmethod    
    def removeitem (intIDDel): 
        """Function to allow users to remove item from the table
     
         Args:
             intIDdel: the ID number of the record user want to delete
     
         Returns:
             None.
        """
        # TODone move processing code into function
        intRowNr = -1
        blnCDRemoved = False
        for row in lstTbl:
            intRowNr += 1
            if row['ID'] == intIDDel:
                del lstTbl[intRowNr]
                blnCDRemoved = True
                break
        if blnCDRemoved:
            print('The CD was removed')
        else:
            print('Could not find this CD!')
                
    @staticmethod
    def savedata ():
        """Function to allow users to save data to the table
     
         Args:
             None.
     
         Returns:
             None.
        """
        objFile = open(strFileName, 'w')
        for row in lstTbl:
                lstValues = list(row.values())
                lstValues[0] = str(lstValues[0])
                objFile.write(','.join(lstValues) + '\n')
        objFile.close()
    


class FileProcessor:
    """Processing the data to and from text file"""

    @staticmethod
    def read_file(file_name, table):
        """Function to manage data ingestion from file to a list of dictionaries

        Reads the data from file identified by file_name into a 2D table
        (list of dicts) table one line in the file represents one dictionary row in table.

        Args:
            file_name (string): name of file used to read the data from
            table (list of dict): 2D data structure (list of dicts) that holds the data during runtime

        Returns:
            None.
        """
        table.clear()  # this clears existing data and allows to load data from file
        try:
            objFile = open(file_name, 'r')
            for line in objFile:
                data = line.strip().split(',')
                dicRow = {'ID': int(data[0]), 'Title': data[1], 'Artist': data[2]}
                table.append(dicRow)
            objFile.close()
        except: 
            print ('No such file')
            

    @staticmethod
    def write_file(file_name, table):
        # TODOne Add code here 
        # TODOne add docstring
        """Function to manage writing data from user input to file 
        
        For each row in the table, a datarow is a dictionary 
        
        Args: 
            file_name (string): name of file used to read the data from
            table (list of dict): 2D data structure (list of dicts) that holds the data during runtime
        
        Returns:
            None.
        """
            
        objFile = open(file_name, 'a')
        for row in table:
            datarow = '{}{}{}'.format (row['ID'],row['Title'],row['Artist'])
            objFile.write (datarow)
        objFile.close()


# -- PRESENTATION (Input/Output) -- #

class IO:
    """Handling Input / Output"""

    @staticmethod
    def print_menu():
        """Displays a menu of choices to the user

        Args:
            None.

        Returns:
            None.
        """

        print('Menu\n\n[l] load Inventory from file\n[a] Add CD\n[i] Display Current Inventory')
        print('[d] delete CD from Inventory\n[s] Save Inventory to file\n[x] exit\n')

    @staticmethod
    def menu_choice():
        """Gets user input for menu selection

        Args:
            None.

        Returns:
            choice (string): a lower case sting of the users input out of the choices l, a, i, d, s or x

        """
        choice = ' '
        while choice not in ['l', 'a', 'i', 'd', 's', 'x']:
            choice = input('Which operation would you like to perform? [l, a, i, d, s or x]: ').lower().strip()
        print()  # Add extra space for layout
        return choice

    @staticmethod
    def show_inventory(table):
        """Displays current inventory table


        Args:
            table (list of dict): 2D data structure (list of dicts) that holds the data during runtime.

        Returns:
            None.

        """
        print('======= The Current Inventory: =======')
        print('ID\tCD Title (by: Artist)\n')
        for row in table:
            print('{}\t{} (by:{})'.format(*row.values()))
        print('======================================')

    # TODOne add I/O functions as needed
    @staticmethod
    def userinput ():
        """Function to ask user for input of new records
     
         Args:
             None.
     
         Returns:
             id: ID number for the new record
             title: Title name for new record 
             artist: Artist name of the new record 
        """
        # TODone move IO code into function
        while True:
            id = input('Enter ID: ').strip()
            try: 
                intID = int(id)
                title = input('What is the CD\'s title? ').strip()
                artist = input('What is the Artist\'s name? ').strip()
                return intID, title, artist
            except: 
                print ('The ID you entered is not an integer')
        
    
        
# 1. When program starts, read in the currently saved Inventory
FileProcessor.read_file(strFileName, lstTbl)

# 2. start main loop
while True:
    # 2.1 Display Menu to user and get choice
    IO.print_menu()
    strChoice = IO.menu_choice()

    # 3. Process menu selection
    # 3.1 process exit first
    if strChoice == 'x':
        break
    # 3.2 process load inventory
    if strChoice == 'l':
        print('WARNING: If you continue, all unsaved data will be lost and the Inventory re-loaded from file.')
        strYesNo = input('type \'yes\' to continue and reload from file. otherwise reload will be canceled')
        if strYesNo.lower() == 'yes':
            print('reloading...')
            FileProcessor.read_file(strFileName, lstTbl)
            IO.show_inventory(lstTbl)
        else:
            input('canceling... Inventory data NOT reloaded. Press [ENTER] to continue to the menu.')
            IO.show_inventory(lstTbl)
        continue  # start loop back at top.
        
    # 3.3 process add a CD
    elif strChoice == 'a':
        # 3.3.1 Ask user for new ID, CD Title and Artist
        # TODO move IO code into function
        #strID = input('Enter ID: ').strip()
        #strTitle = input('What is the CD\'s title? ').strip()
        #stArtist = input('What is the Artist\'s name? ').strip()
        strID, strTitle, stArtist = IO.userinput()
        
        # 3.3.2 Add item to the table
        # TODO move processing code into function
        #intID = int(strID)
        #dicRow = {'ID': intID, 'Title': strTitle, 'Artist': stArtist}
        #lstTbl.append(dicRow)
        #IO.show_inventory(lstTbl)
        DataProcessor.additem(strID, strTitle, stArtist)
        IO.show_inventory(lstTbl)
        continue  # start loop back at top.
        
    # 3.4 process display current inventory
    elif strChoice == 'i':
        IO.show_inventory(lstTbl)
        continue  # start loop back at top.
        
    # 3.5 process delete a CD
    elif strChoice == 'd':
        # 3.5.1 get Userinput for which CD to delete
        # 3.5.1.1 display Inventory to user
        IO.show_inventory(lstTbl)
        # 3.5.1.2 ask user which ID to remove
        intIDDel = int(input('Which ID would you like to delete? ').strip())
        # 3.5.2 search thru table and delete CD
        # TODOne move processing code into function
        DataProcessor.removeitem (intIDDel) 
        IO.show_inventory(lstTbl)
        continue  # start loop back at top.
        
    # 3.6 process save inventory to file
    elif strChoice == 's':
        # 3.6.1 Display current inventory and ask user for confirmation to save
        IO.show_inventory(lstTbl)
        strYesNo = input('Save this inventory to file? [y/n] ').strip().lower()
        # 3.6.2 Process choice
        if strYesNo == 'y':
            # 3.6.2.1 save data
            # TODOne move processing code into function
            DataProcessor.savedata ()
        else:
            input('The inventory was NOT saved to file. Press [ENTER] to return to the menu.')   
        continue  # start loop back at top.
        
    # 3.7 catch-all should not be possible, as user choice gets vetted in IO, but to be save:
    else:
        print('General Error')