Alphabetically sort with Python?-CodePudding

I am aware of the sorted() function but I am having a little trouble using it/implementing it in my code. I have a database containing student records such as Name, address, age etc. When the user selects "4" the program runs the function to Display all records saved in the database and I desire it to be sorted alphabetically. My function works and displays the records, just not alphabetically. How could I take advantage of the sorted() function to make my code display the records alphabetically? Any help would be greatly appreciated.

rom ShowAllRecords import show_record
from deleteRecord import delete_student
from showRecord import view_records
from createRecord import add_record
global student_info
global database

"""
Fields :- ['Student ID', 'First name', 'Last Name', 'age', 'address', 'phone number']
1. Create a new Record
2. Show a record
3. Delete a record
4. Display All Records.
5. Exit
"""


student_info = ['Student ID', 'First name', 'last name', 'age', 'address', 'phone number']
database = 'file_records.txt'


def display_menu():
    print("**********************************************")
    print("             RECORDS MANAGER    ")
    print("**********************************************")
    print("1. Create a new record. ")
    print("2. Show a record. ")
    print("3. Delete a record. ")
    print("4. Display All Records. ")
    print("5. Exit")


while True:
    display_menu()

    choice = input("Enter your choice: ")
    if choice == '1':
        print('You have chosen "Create a new record."')
        add_record()
    elif choice == '2':
        print('You have chosen "Show a record"')
        show_record()
    elif choice == '3':
        delete_student()
    elif choice == '4':
        print('You have chosen "Display ALL records"')
        view_records()
    else:
        break


print("**********************************************")
print("             RECORDS MANAGER                  ")
print("**********************************************")

ViewRecords function-

import csv
student_info = ['Student ID', 'First name', 'last name', 'age', 'address', 'phone number']
database = 'file_records.txt'


def view_records():
    global student_info
    global database

    

    print("--- Student Records ---")

    with open(database, "r", encoding="utf-8") as f:
        reader = csv.reader(f)
        for x in student_info:
            print(x, end='\t |')
        print("\n-----------------------------------------------------------------")

        for row in reader:
            for item in row:
                print(item, end="\t |")
            print("\n")

    input("Press any key to continue")

I know I should use the sorted function, just not sure where/how to properly implement it within my code

Sample Run:

Blockquote

          RECORDS MANAGER

    1. Create a new record.
    2. Show a record.
    3. Delete a record.
    4. Display All Records.
    5. Exit.

Enter your option [1 - 5]: 4 You have chosen "Display ALL records in alphabetical order by last name." Would you like the registry sorted alphabetically in Ascending or Descending order? (A or D): D

Last Name: Hunt First Name: Alan Student ID: 875653 Age: 23 Address: 345 Ocean Way Phone number: 3334445454

Last Name: Farrow First Name: Mia Student ID: 86756475 Age: 22 Address: 34 Lotus Ct Phone number: 9994448585

Done! Press enter to continue. returning to Main Menu.

CodePudding user response：

You already know you need the sorted function. Think about what you need to sort: all the records in your csv file, and the key to use to sort: Let's say by last name and then first name. See the documentation for more detail on the key argument to sorted. Since you want to sort by two items, you can create a tuple containing these two items as your key. In this case, for any student record r, the last name is the third element (r[2]) and the first name is the second element (r[1]), so our key needs to be the tuple (r[2], r[1]).

So in the function where you read the records, instead of printing them immediately, read all the records first, then sort them, and then print them:

def view_records():
    # These are not necessary since you never set these variables in the function
    # You can access those variables without global
    # global student_info
    # global database

    print("--- Student Records ---")

    with open(database, "r", encoding="utf-8") as f:
        for x in student_info:
            print(x, end='\t |')
        print("\n-----------------------------------------------------------------")

        reader = csv.reader(f)
        student_records = sorted(reader, key=lambda r: (r[2], r[1]))
        for row in student_records:
            print(*row, sep="\t |")

    input("Press any key to continue")

CodePudding user response：

By default the sorted() function will sort a list alphabetically, so you could read the lines in the file into a list, call sorted on the list, the print that list line by line with something like this:

with open(database, "r", encoding="utf-8") as f:
        reader = csv.reader(f)

        # make a list of all lines in the database
        line_list = []
        for line in reader:
            line_list.append(line)

        # print the list
        line_list = sorted(line_list)
        for line in line_list:
           print(line)

I'm not exactly sure that's the correct way to go line by line for a database file but you get the idea. Another thing you can do with sorted is pass it a function that determines exactly what you sort, so say if you have 3 columns in your database and for each line you split the row into a list of 3 items you could do this:

def func(x):
    return x[2]

data = [[a,b,c],[d,e,f],[g,h,i]]
sorted_data = sorted(data, key=func)

to sort the data by the third column. This is also used when you want to sort by some manner that's not alphanumeric.

Finally, for questions on basic functions like this I highly recommend geeksforgeeks as it usually has good basic examples and descriptions of things like this.