File handling – Binary file operations in Python – Search, Append, Update and Delete Records

1. Open the file in append mode using “ab”  Ex.: f = open (“file.dat”,”ab”)
2. Enter data to append
3. Append entered data into the dictionary/list object
4. Use pickle.dump() method to write the dictionary/list data
5. Close the file

def bf_append():
    f = open("sports.dat","ab")
    print("Append Data")
    pcode = int(input("Enter the Player code:"))
    pname = input("Enter Player Name:")
    score = int(input("Enter individual score:"))
    rank = int(input("Enter Player Rank:"))
    rec={'Pcode':pcode,'Pname':pname,'Score':score,'Rank':rank}
    pickle.dump(rec,f)
    f.close()
bf_append()

Do not run your code without reading the contents.

Reading Data

1. Open the file in read mode using “rb” Ex.: f = open(“File.dat”, “rb”)
2. Use while loop with True statement to read the entire contents of the file individually.
3. Use try – except for Exception handling to avoid runtime EOFError
4. Now load data into an object through the load function
5. Print data as per need
6. Close the file

Observe the following code:

  def bf_read():
    f = open("Sports.dat","rb")
    print("*"*78)
    print("Data stored in File....")
    while True:
       try:
            rec= pickle.load(f)
            print("Player Code:",rec['Pcode'])
            print("Player Name:",rec['Pname'])
            print("Individual Score:",rec['Score'])
            print("Player Rank:",rec['Rank'])
            print("."*78)
       except Exception:
         break
    f.close()
bf_read() 

1. 1. Open the file in reading mode using “rb”
   2. Prompt a message to ask unique field from data to search
   3. Declare a boolean variable flag to store False for the record not found and True when the record found
   4. Use a while loop to access records individually
   5. Now load the data into the dictionary object using load() function
   6. Use if condition to compare the data with the variable taken in step 2
   7. Print the record found
   8. Assign True to the flag variable declared in step 3
   9. Use the except block to handle EOFError and terminate the loop using the break
   10. Print record not found message when Flag is False
   11. Finally, close the file using f.close()

Observe the following code:

def bf_search():
    f = open("Sports.dat","rb")
    pc = int(input("Player to code to search:"))
    flag=False
    while True:
        try:
            rec= pickle.load(f)
            if rec['Pcode']==pc:
                    print("Player Name:",rec['Pname'])
                    print("Individual Score:",rec['Score'])
                    print("Rank:",rec['Rank'])
                    flag = True
         except Exception:
             f.close()
    if flag==False:
        print("Record not found...")
    f.close()
bf_search()

1. 1. Open the file using read mode
   2. Declare a variable for unique value to be updated
   3. Use try-except and while loop as explained above
   4. Add record fetched from binary file into a list
   5. Enter the new record information to update
   6. Compare the fetched records with entered record and assign the new values to update
   7. Write the data using dump() function
   8. Close the file

Have look at the following code:

def bf_update():
  f = open('student.dat','rb')
  reclst = []
  while True:
     try:
       rec = pickle.load(f)
       reclst.append(rec)
     except EOFError:
        break
  f.close()
pc=int(input("Enter player code to update:"))
pn=input("Enter new name:")
ps=int(input("Enter Player Score:"))
pr=int(input("Enter Player Rank:"))
for i in range (len(reclst)):
    if reclst[i]['Pcode']==pc:
       reclst[i]['Pname'] = pn
       reclst[i]['Score'] = ps
       reclst[i]['Rank'] = pr
f = open('sports.dat','wb')
for i in reclst:
    pickle.dump(i,f)
f.close() 
bf_update()

1. 1. Open the file in reading mode
   2. Load data using the load function
   3. Close file
   4. Prompt a message to delete a record with a variable
   5. Open file in writing mode
   6. Declare a list object to store data from the file
   7. Use for loop and if condition as used in the update
   8. Now in if condition write continue if the record is found
   9. Write data using the dump method
   10. Close the file

Observe this code (Assume the Pickle module is included):

def bf_delete():
   f = open('sports.dat','rb')
   reclst = []
   while True:
      try:
      rec = pickle.load(f)
      reclst.append(rec)
      except EOFError:
          break
  f.close()
  pc=int(input("Enter Player code to delete record:"))
  f = open('sports.dat','wb')
  for i in reclst:
      if i['Pcode']==pc:
         continue
      pickle.dump(x,f)
  f.close() 
bf_delete()