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GRADE XII - BINARY FILES | 22 Aug

 

Write & Read a List to a Binary File

import pickle

my_list = [10, 20, 30, 40, 50]

file = open("data.dat", "wb")  # open file in write-binary mode

pickle.dump(my_list, file)     # write the list to the file

file.close()                   # don't forget to close the file

print("List successfully written to binary file.")

read-binary mode

file = open("data.dat", "rb")   # open file in read-binary mode

loaded_list = pickle.load(file)  # read the list from the file

file.close()

print("List read from binary file:", loaded_list)


Notes:

  • wb = write binary
  • rb = read binary
  • pickle.dump(obj, file) → writes object to file

pickle.load(file) → reads object from file


Write a Dictionary to a Binary File

import pickle

# Dictionary to write

my_dict = {

    "name": "Pooja",

    "age": 25,

    "city": "Delhi"

}

# Open file in write-binary mode

file = open("data.dat", "wb")

pickle.dump(my_dict, file)  # Serialize and write dictionary

file.close()

print("Dictionary successfully written to binary file.")

 

file = open("data.dat", "rb")

loaded_dict = pickle.load(file)  # Deserialize

file.close()

print("Dictionary read from file:", loaded_dict)

EG: DUMP & LOAD USING BINARY FILE

import pickle

file = open("stud.dat", "wb")

while True:

    rno = int(input("\nEnter roll no - "))

    name = input("Enter name - ")

    perc = float(input("Enter percentage - "))

    stream = input("Enter stream - ")

    dets = [rno, name, perc, stream]

    pickle.dump(dets, file)

 

    ans = input("Want to enter another (y/n) - ")

    if ans in "nN":

        break

file.close()

print("Student records saved successfully.")

 

file = open("stud.dat", "rb")

print("Student Records:\n")

while True:

    try:

        record = pickle.load(file)  # Load one record at a time

        print("Roll No:", record[0])

        print("Name:", record[1])

        print("Percentage:", record[2])

        print("Stream:", record[3])

        print("-" * 30)

    except EOFError:

        break  # End of file reached

file.close()

28th July 2025

Eg: Updated Code to Add Multiple Records Without Overwriting:

import pickle

file = open("stud.dat", "ab")  # Append binary mode

while True:

    rno = int(input("\nEnter roll no - "))

    name = input("Enter name - ")

    perc = float(input("Enter percentage - "))

    stream = input("Enter stream - ")

     dets = [rno, name, perc, stream]

    pickle.dump(dets, file)

    ans = input("Want to enter another (y/n) - ")

    if ans in "nN":

        break

file.close()

print("Student records added successfully.")

 

READ FILE :

try:

    file = open("stud.dat", "rb")  # Open in read-binary mode

    print("Student Records:\n")

    while True:

        try:

            record = pickle.load(file)  # Load one record at a time

            print("Roll No:", record[0])

            print("Name:", record[1])

            print("Percentage:", record[2])

            print("Stream:", record[3])

            print("-" * 30)

        except EOFError:

            break  # End of file reached

    file.close()

except FileNotFoundError:

    print("File not found. Please make sure 'stud.dat' exists.")


Q1. a)WAP that reads a binary file “emp” and display all records of employee one by one.

       b) Display all records who are getting salaries between 2500  and 300

Sol:

import pickle

my_list = [100, 202, 300, 400, 500]

# Write the list to a binary file

with open("data.dat", "wb") as file:

    pickle.dump(my_list, file)

print("List successfully written to binary file.")

 

f1=open("data.dat", "rb")

e=pickle.load(f1)

for x in e:

     print(x)

f1.close()

PART B

f1=open("data.dat", "rb")

e=pickle.load(f1)

for x in e:

        if x >= 200 and x <= 400:

        print(x)

Q2.

1. 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:

a)     Create() – to input data for passengers and write it in the binary file PASSENGERS.DAT.

b)    SearchDestn(D) – to read contents from the file PASSENGERS.DAT and display the details of those passengers whose DESTN matches with the value of D.

c)     UpdateFare() – to increase the fare of all passengers by 5% and rewrite the updated records into the file PASSENGERS.DAT.

 

  2. Consider a binary file, items.dat, containing records stored in the given format:

{item_id: [item_name, amount]}

Write a function, Copy_new(), that copies all records whose amount is greater than 1000 from items.dat to new_items.dat.

 

3. A binary file, EMP.DAT, has the following structure:

[Emp_Id, Name, Salary]

Where:

  • Emp_Id : Employee ID
  • Name : Employee Name
  • Salary : Employee Salary

Write a user-defined function disp_Detail() that would read the contents of the file EMP.DAT and display the details of those employees whose salary is below 25000.

 4. A binary file named “TEST.dat” has some records of the structure:

[TestId, Subject, MaxMarks, ScoredMarks].

Write a function in Python named DisplayAvgMarks(Sub) that will accept a subject as an argument and read the contents of TEST.dat. The function will calculate & display the Average of the ScoredMarks of the passed Subject on screen.

  

SOLUTIONS

 1. 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:

a)     Create() – to input data for passengers and write it in the binary file PASSENGERS.DAT.

b)    SearchDestn(D) – to read contents from the file PASSENGERS.DAT and display the details of those passengers whose DESTN matches with the value of D.

c)     UpdateFare() – to increase the fare of all passengers by 5% and rewrite the updated records into the file PASSENGERS.DAT.

Sol.

        import pickle

 

# a) Function to create and write passenger data

def Create():

    with open("PASSENGERS.DAT", "wb") as file:

        while True:

            pnr = input("Enter PNR: ")

            pname = input("Enter Passenger Name: ")

            brdstn = input("Enter Boarding Station: ")

            destn = input("Enter Destination Station: ")

            fare = float(input("Enter Fare: "))

            record = [pnr, pname, brdstn, destn, fare]

            pickle.dump(record, file)

           

            choice = input("Add another record? (y/n): ")

            if choice.lower() != 'y':

                break

 

# b) Function to search passengers by destination

import pickle

 

def SearchDestn(D):

    try:

        with open("PASSENGERS.DAT", "rb") as file:

            count = 0  # Counter for matching records

            while True:

                try:

                    record = pickle.load(file)

                    if record[3].lower() == D.lower():

                        print("PNR:", record[0])

                        print("Name:", record[1])

                        print("Boarding:", record[2])

                        print("Destination:", record[3])

                        print("Fare:", record[4])

                        print("-" * 30)

                        count += 1

                except EOFError:

                    break

            if count == 0:

                print("No passengers found with destination:", D)

    except FileNotFoundError:

        print("PASSENGERS.DAT file not found.")

 

# c) Function to update fare by 5%

def UpdateFare():

    try:

        updated_records = []

        with open("PASSENGERS.DAT", "rb") as file:

            while True:

                try:

                    record = pickle.load(file)

                    record[4] *= 1.05  # Increase fare by 5%

                    updated_records.append(record)

                except EOFError:

                    break

 

        with open("PASSENGERS.DAT", "wb") as file:

            for rec in updated_records:

                pickle.dump(rec, file)

        print("Fare updated successfully for all passengers.")

 

    except FileNotFoundError:

        print("File not found.")

 

 2. Consider a binary file, items.dat, containing records stored in the given format:

{item_id: [item_name, amount]}

Write a function, Copy_new(), that copies all records whose amount is greater than 1000 from items.dat to new_items.dat.

 

Sol.

import pickle

 def Copy_new():

    try:

        with open("items.dat", "rb") as infile, open("new_items.dat", "wb") as outfile:

            while True:

                try:

                    record = pickle.load(infile)

                    # Check each item in the dictionary

                    for item_id, value in record.items():

                        item_name, amount = value

                        if amount > 1000:

                            pickle.dump({item_id: value}, outfile)

                except EOFError:

                    break

    except FileNotFoundError:

        print("File not found.")

 

3. A binary file, EMP.DAT, has the following structure:

[Emp_Id, Name, Salary]

Where:

  • Emp_Id : Employee ID
  • Name : Employee Name
  • Salary : Employee Salary

Write a user-defined function disp_Detail() that would read the contents of the file EMP.DAT and display the details of those employees whose salary is below 25000.

 Sol.

import pickle

def disp_Detail():

    try:

        with open("EMP.DAT", "rb") as file:

            print("Employees with salary below 25000:")

            while True:

                try:

                    emp = pickle.load(file)

                    if emp[2] < 25000:

                        print("Emp_ID:", emp[0], ", Name:", emp[1], ", Salary:", emp[2])

                except EOFError:

                    break

    except FileNotFoundError:

        print("EMP.DAT file not found.")

 DICTIONARY METHOD:

import pickle

def add_Employee():

    file = open("EMP.DAT", "ab")   # append binary mode

    ch = 'y'

        while ch.lower() == 'y':

        emp = {}

        emp["Emp_Id"] = int(input("Enter Employee ID: "))

        emp["Name"] = input("Enter Name: ")

        emp["Salary"] = float(input("Enter Salary: "))

                pickle.dump(emp, file)

                ch = input("Add more records? (y/n): ")

     file.close()


def disp_Detail():

    try:

        with open("EMP.DAT", "rb") as file:

            print("Employees with salary below 25000:")

            while True:

                try:

                    emp = pickle.load(file)   # emp is a dictionary

                    if emp["Salary"] < 25000:

                        print("Emp_ID:", emp["Emp_Id"], ", Name:", emp["Name"], ", Salary:", emp["Salary"])

                except EOFError:

                    break

    except FileNotFoundError:

        print("EMP.DAT file not found.")


4. 4. A binary file named “TEST.dat” has some records of the structure:

 [TestId, Subject, MaxMarks, ScoredMarks].

Write a function in Python named DisplayAvgMarks(Sub) that will accept a subject as an argument and read the contents of TEST.dat. The function will calculate & display the Average of the ScoredMarks of the passed Subject on screen.

 Sol.

import pickle

def DisplayAvgMarks(Sub):

    try:

        with open("TEST.dat", "rb") as file:

            total = 0

            count = 0

            while True:

                try:

                    record = pickle.load(file)

                    if record[1].lower() == Sub.lower():  # Match subject

                        total += record[3]  # ScoredMarks

                        count += 1

                except EOFError:

                    break


        if count > 0:

            avg = total / count

            print("Average Scored Marks in", Sub, "=", round(avg, 2))

        else:

            print("No records found for subject:", Sub)


    except FileNotFoundError:

        print("TEST.dat file not found.")

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