How to Write data into a Binary File in Python | Writing data into a binary file using Python

To write an object  to a binary file opened in the write mode, we should use dump( ) function of pickle module as per the following syntax :

pickle.dump(<object>, <file-handler>)

For example, if you have a file open in handle f1 as

f1=open(“file1.txt”,”wb”)

1. Python program to write a list namely list1 in the file named file1.txt

import pickle
f1=open("file1.txt","wb")
list1=[1,'Lovejot','Teacher']
pickle.dump(list1,f1)
f1.close()

2. Python program to write a tuple namely t1 in the file named file2.txt

import pickle
f2=open("file2.txt","wb")
t1=(2,'Sumit','XII']
pickle.dump(t1,f2)
f2.close()

3. Python program to write a dictionary namely d1 in the file named file3.txt

import pickle
f3=open("file3.txt","wb")
d1={'Rollno':1, name:'Anil'}
pickle.dump(d1,f3)
f3.close()

4. Python program to create a binary file named employee.dat and write details of employees available in the form of dictionaries.

import pickle

# dictionary objects
E1={ ‘Empno’ :101, ‘Name’ : ‘Ramesh’  , ‘Salary’ : 17000}
E2={ ‘Empno’ :102, ‘Name’ : ’’ , ‘Age’ : 30, ‘Salary’ : 18000}

#open file in write mode
file1 = open (‘Employee.dat’ , ‘wb’)

#write to the file
pickle.dump (E1 ,file1)
pickle.dump (E2 , file1)

#close file
file1.close( )                             

5. Python program to  create a binary file named student.dat . Data of students must be put at run time then it should be stored in file. The structure of data is (rollno, name, marks).

import pickle
s={ }                                #declare empty dictionary
file2 = open(‘student.dat’ , ‘wb’)                 #open file
R = int (input (“Enter roll number=“ ) )
N = input (“Enter name =“ )
M = float(input (“Enter marks =“ )

# add read data into dictionary
S [‘Rollno’] = R
S [‘Name’] = N
S[‘Marks’]  = M

# now write into the file
pickle.dump (s ,file2)

file2.close( )                

Appending Records in Binary File in Python

Appending records in binary files is similar to writing record but there are two differences:

i. We need to open binary file in append mode (“ab”).
ii. If file doesn’t exit, it will create a new file .
iii. If file already exits, it will write new record at the end of existing file.

# Python program to append a list namely list1 in the file named file1.txt

import pickle
f1=open("file1.txt","ab")
list1=[2,'Ayush','Student']
pickle.dump(list1,f1)
f1.close()

#Python program to  append a tuple namely t1 in the file named file2.txt

import pickle
f2=open("file2.txt","ab")
t1=(3,'Sunita','XI']
pickle.dump(t1,f2)
f2.close()

#Python program to append a dictionary namely d1 in the file named file3.txt

import pickle
f3=open("file3.txt","ab")
d1={'Rollno':2, name:'Sumit'}
pickle.dump(d1,f3)
f3.close()

#Python program to append student records to an existing file student.dat by getting input from user.

import pickle
Students ={ }  #empty dictionary created to store records
file1 = open ('Student.dat', 'ab')

choice = 'y'

while choice == 'y' :
     #Read values of rollno, name and marks
     R=int(input("Enter roll number of student = ")) 
     N=input("Enter name =")
     M=float (input("Enter marks = "))

     #put values of variables R,N, M in dictionary
     Students['Rollno'] =R
     Students['Name'] =N
     Students['Marks'] =M

     pickle.dump (Students, file1) #Write record into the file

     choice=input("Do you want to add more records (y/n))

file1.close( )

Output

Enter roll number of student = 101
Enter name =anita
Enter marks = 88
Do you want to add more records (y/n)…y
Enter roll number of student = 102
Enter name =sunil
Enter marks = 56
Do you want to add more records (y/n)n

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