# A CSV FILE IS A 2D GRID OF DATA. IT IS A VERY VERSATILE STORAGE FORMAT.
# Within Python, this same structure is represented as a nested list.
# Each sublist of the nested list represents a row from the csv file

# The general process for using a csv file for storage with Python is:
# 1) Use Python to open the file and read all data from it into a nested list
# 2) Edit the data within the Python list according to need.
# 3) Write the data back to the file again

import csv # the csv library contains code for handling csv files.

rows = [] # creates an empty list called "rows"

# OPEN A CSV FILE CALLED mycsvfile.csv (or CREATE if it doesn't exist) AND WRITE TO IT -------------------------

with open('mycsvfile.csv', 'w', newline="") as csvfile: # "w" is for writing,
    # newline= ensures that each row written terminates correctly
    # the With statement will close the file as soon as everything indented is completed
    print("Adding contents to 'mycsvfile.csv' file...\n ")
    csv_file= csv.writer(csvfile) # uses the writer method
    csv_file.writerow (['Surname','First name','Date of Birth']) # writes the header row to the file using a list
    csv_file.writerow (['Smith', 'John', '11-Dec-2004']) # writes a data row to the file using a list
    csv_file.writerow (['Banana', 'Fred', '11-Jan-2000']) # writes a 2nd data row to the file using a list
    # writes multiple rows to the file using a nested list
    csv_file.writerows ([['Fishface', 'Carol', '11-Feb-2003'],['Picklechin', 'Peter', '16-Feb-2007']])

# READ FROM CSV FILE mycsvfile.csv AND PRINT OFF EACH ROW OF DATA ----------------

with open('mycsvfile.csv', 'r') as csvfile: # "r" is for reading
    csv_file= csv.reader(csvfile) # uses the reader method
    print("\nPrinting contents of 'mycsvfile.csv' file...\n")
    for row in csv_file: # for each row in the file
        print(row) # each row can be obtained as a list or....
        print (', '.join(row)) # joins together individual data items on a row with ", " in between and prints them

# READ FROM CSV FILE mycsvfile.csv AND PRINT OFF ALL ROWs OF DATA AS A LIST of LISTS ----------------

print("Putting 'mycsvfile.csv' file into a list...\n")
with open('mycsvfile.csv', 'r') as csvfile: # uses the reader method
    rows = list(csv.reader(csvfile))
print(rows)

print("Printing out the full list, list by list:\n")
for row in rows: # for each row of data now stored in the list called "rows"
    print(row) # print each row

# THE LIST rows IS A 2D ARRAY. ITEMS CAN BE ACCESSED USING TWO INDICES. FOR EXAMPLE...

print("\nAccessing a single element from the list:\n")
print(rows[1][1])

print("\nHere is an example:\n")
print("First name: ", rows[1][1])
print("Surname: ", rows[1][0])
print("DOB: ", rows[1][2])