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Python: Orders Manager P3



Learning : Orders Management System using Python and Pandas
Subject: Data File and Adding new Record

In This system and once the user run the application we will check if the Data file exists or not. If the file exists then the system will run, otherwise the application will guide the user to some questions to create the new file. Then we will talk about adding new records to our file.

First time run: Each time we run the application the system will chick for the file, at this version we will have only one data file we will call it “orders_dataframe.csv” if the file exists the application will continue and the file will be loaded automaticly, if not, then the first choice of our menu will be called. Function called “create_file()” will run, we will inform the user that the file is not there and if he want to create a new file. If the user select Yes, the file will be created and a dummy row (id = 0) will be added. If the user select No, we will show a message then if any key pressed the system will quite. .. Let’s see the code ..

File Exists check point
def file_exists():

# Check if the data file not exists create one

if not (os.path.exists(‘orders_dataframe.csv’)):

no_file =’o’

while no_file not in [‘y’,’Y’,’n’,’N’]: # Validation for user input

clear() # To clear the terminal.

app_header()

no_file = input(‘\n The file ”orders_dataframe.csv” is not exists, Do you want to create new one: [ y , n ] ‘)

if no_file in [‘y’,’Y’]: # Validation for user input

create_file() # Call the function create_file

return

elif no_file in [‘n’,’N’]: # Validation for user input

print(‘\n You select not to create a data file, so the system will Exit. ‘)

input(‘\n\n Press any key …’)

return ‘exit’


Validation:
To keep asking the user for his input until he enters one of [ y,Y,n,N]

while no_file not in [‘y’,’Y’,’n’,’N’]:

no_file = input(‘\n The file ”orders_dataframe.csv” is not exists, Do you want to create new one: [y,n] ‘)


Last, I am thinking to add a header for our app, so this header will be at the top of all out screens. Here it is ..

Application Header
def app_header():

print(‘\n ********************************’)

print(‘ ** Orders Managment System **’)

print(‘ ** App V.08-19 **’)

print(‘ **********************************\n’)


In the next post we will look at the Validation on the File Exists check and create file function, also first row added to our dataframe.



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