How to Read data from a Binary File in Python | Searching record from a binary file in Python

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How to Read data from a Binary File in Python | Reading data from binary file in Python

After writing data into binary file using dump() method of pickle module, we can read and display content of binary file load( ) method of the pickle module. Reading data from binary file is known as unpickling.

The syntax of load( ) method is

<object> =pickle.load(<filehandle>)

#Program to read and display data stored in binary file Employee.dat as created in program 4 given in previous post.

import pickle
Emp = {}  #Empty dictionary object to stored records read from Employee.data
Empfile = open('Employee.dat', 'rb')   #open binary file in read mode
try:
     while True :                  # It will become False upon EOF
          Emp = pickle.load(F)   #Read record in Emp dictionary from file handle Empfile
          print (Emp)              # print the record
except EOFError :
     Empfile.close()   

Output

{ ‘Empno’ :101, ‘Name’ : ‘Ramesh’, ‘Age’ : 40, ‘Salary’ : 17000}
{ ‘Empno’ :102, ‘Name’ : ’Mohan’ , ‘Age’ : 30, ‘Salary’ : 18000}

#Program  to create a binary file named myfile.dat and store a string value in it.

import pickle
S =”This is string value”
with open(“myfile.dat”, “wb”) as f :
     pickle.dump (S,f)
print(“file successfully created.”)
f.close()

Above program created a binary file namely myfile.dat that stored the string variable S in  binary format.

# Program to read data from the file myfile.dat created in previous program and display all the text before the letter ‘v’,

import pickle
S = ‘‘
with open (“myfile.dat”, “rb”)as f :
     S = pickle.load(fh)
     S1 =S.split(‘v’)
print(S1[0])
f.close()

 Output

This is string

Searching record from a binary file in Python

To search something in a file, we need to follow given steps:

  1. Open the file in read mode.
  2. Read the contents of file record by record
  3. Look for the desired item in record.
  4. If found, “Value is found”.
  5. If not found, read the next record and look for the desired item.
  6. If desired item is not found in any of the records, “No such item found“.

# Program to open file Employee.dat containing following records. Search for records with Empno=101. If found, display the record.

{‘Empno’ :101, ‘Name’ : ‘Ramesh’, ‘Age’ : 40, ‘Salary’ : 17000} 
{‘Empno’ :102, ‘Name’ : ’Mohan’ , ‘Age’ : 30, ‘Salary’ : 18000}

 

import pickle
emp ={ }     # empty dictionary object to hold records
found = False
F = open(‘Employee.dat’, ‘rb’)    # open binary file in read mode
try :
  print (“Searching in file Employee.dat… “)
  while True:     # It will become False upon EOF(End of file) exception
     emp=pickle.load(F) #read record in emp dictionary from file handle F
     if emp[‘Empno’]==101:     
         print (emp)                  #print the record
         found = True
except EOFError :
   if found == False :
     print (“No such records found in the file “)
   else :
     print(“Search successful.”)
F.close( )                                #close file

 Output

Searching in file stu.dat…
{‘Empno’ :101, ‘Name’ : ‘Ramesh’, ‘Age’ : 40, ‘Salary’ : 17000}
Search successful.

 # Program to open file Employee.dat containing following records. Search for records with age>30. If found, display the record.

{‘Empno’ :101, ‘Name’ : ‘Ramesh’, ‘Age’ : 40, ‘Salary’ : 17000}
{‘Empno’ :102, ‘Name’ : ’Mohan’ , ‘Age’ : 30, ‘Salary’ : 18000}

import pickle
emp ={}     # empty dictionary object to hold records
found = False
F = open(‘Employee.dat’, ‘rb’)    # open binary file in read mode
try :
  print (“Searching in file Employee.dat… “)
  while True:     # It will become False upon EOF(End of file) exception
     emp=pickle.load(F) #read record in emp dictionary from file handle F
     if emp[‘Age’]>30:     
         print (emp)                  #print the record
         found = True
except EOFError :
   if found == False :
     print (“No such records found in the file “)
   else :
     print(“Search successful.”)
F.close( )                                #close file

 Output

Searching in file stu.dat…
{‘Empno’ :101, ‘Name’ : ‘Ramesh’, ‘Age’ : 40, ‘Salary’ : 17000}
Search successful.

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