Q.A file, PASSENGERS.DAT, stores the records of passengers using the following structure : [PNR, PName, BRDSTN, DESTN, FARE] where : PNR - Passenger Number (string type) PName - Passenger Name (string type) BRDSTN - Boarding Station Name (string type) DESTN - Destination Station Name (string type) FARE - Fare amount for the journey (float type) Write user defined functions in Python for the following tasks :

File Input/Output with Filtering in Python

When working with binary files that store structured records, Python's pickle module lets you serialize and deserialize data. Each passenger record can be stored as a dictionary or list, and the file operations follow a standard pattern: open in the appropriate mode, read or write using pickle.load() and pickle.dump(), then close.

For the Create() function, you repeatedly take input for PNR, PName, BRDSTN, DESTN, and FARE, pack each set into a dictionary, and append it to a list. Once all records are entered, open PASSENGERS.DAT in write-binary mode ('wb') and dump the entire list with pickle.dump(passengers, file).

The SearchDestn(D) function opens the file in read-binary mode ('rb'), loads the list of records with pickle.load(file), then iterates through each passenger dictionary. Whenever the 'DESTN' key matches the parameter D, print that passenger's details. This is a straightforward filtering operation. …

The question asks you to work with a binary file that holds passenger records — a common pattern in file-handling problems where structured data (like a railway reservation system) is stored persistently. Each record is a list or tuple of five fields: PNR, passenger name, boarding station, destination, and fare. You need to write three functions: one to create and populate the file, one to filter and display records by destination, and one to apply a percentage increase to all fares and save the changes back.

Binary files in Python are typically handled using the pickle module, which serializes Python objects (lists, dictionaries, tuples) into a byte stream and deserializes them on reading. Unlike text files, you cannot simply append a line; you read the entire collection of records, modify it in memory, and write it back if updates are needed.

(i) Create() — Writing records to the file

This function repeatedly prompts the user for passenger details and writes each record to PASSENGERS.DAT in binary mode. You open the file in write-binary mode ('wb' or 'ab' if appending), collect the five fields as input, pack them into a list, and use pickle.dump() to serialize and store each record.

import pickle

def Create():
    with open('PASSENGERS.DAT', 'wb') as f:
        while True:
            pnr = input("Enter PNR (or 'stop' to finish): ")
            if pnr.lower() == 'stop':
                break
            pname = input("Enter Passenger Name: ")
            brdstn = input("Enter Boarding Station: ")
            destn = input("Enter Destination: ")
            fare = float(input("Enter Fare: "))
            
            record = [pnr, pname, brdstn, destn, fare]
            pickle.dump(record, f)
    print("Records written successfully.")

Each call to pickle.dump(record, f) writes one record; the loop continues until the user types "stop". The file now contains a sequence of pickled lists, one after another.

(ii) SearchDestn(D) — Filtering by destination

This function reads all records from the file and displays only those whose destination matches the parameter D. You open the file in read-binary mode ('rb'), loop through it using pickle.load() until you hit the end (catching EOFError), and print records where the fourth field equals D.

def SearchDestn(D):
    try:
        with open('PASSENGERS.DAT', 'rb') as f:
            found = False
            while True:
                try:
                    record = pickle.load(f)
                    if record[3] == D:  # DESTN is at index 3
                        print(f"PNR: {record[0]}, Name: {record[1]}, "
                              f"Boarding: {record[2]}, Destination: {record[3]}, "
                              f"Fare: {record[4]}")
                        found = True
                except EOFError:
                    break
            if not found:
                print(f"No passengers found traveling to {D}.")
    except FileNotFoundError:
        print("File PASSENGERS.DAT does not exist.")

The inner try-except EOFError is the standard idiom for reading a pickle file of unknown length: pickle.load() raises EOFError when there are no more objects to read. The outer try-except FileNotFoundError handles the case where the file hasn't been created yet.

(iii) UpdateFare() — Increasing all fares by 5%

This function reads all records, increases each fare by 5%, and writes the modified list back to the file. Because binary files do not support in-place editing of individual records, you must load all records into a list, update them in memory, then rewrite the entire file.

def UpdateFare():
    try:
        with open('PASSENGERS.DAT', 'rb') as f:
            records = [] …