Binary files
=> to store the block of data into binary files
pickle module=> two functions
1. load() => to read data from file
2. dump() => to write data into file
1. write a python function to read empno,ename,salary,deptno
from user and write into emp.dat file continuously
solution:
import pickle
def writebinary():
f1=open("emp.dat","wb")
while True:
empno=int(input("enter the empno"))
ename=input("enter the empname")
salary=int(input("enter the salary"))
deptno=int(input("enter the deptno"))
l1=[empno,ename,salary,deptno]
pickle.dump(l1,f1)
op=input("enter the option to continue or not")
if op=='n':
break
f1.close()
writebinary()
2. write data into emp.dat file in dicitionary format
{"empno":empno,"ename":ename,"salary":salary,"deptno":deptno}
solution:
import pickle
def writebinary():
d1={}
f1=open("empdict.dat","wb")
while True:
empno=int(input("enter the empno"))
ename=input("enter the empname")
salary=int(input("enter the salary"))
deptno=int(input("enter the deptno"))
d1["empno"]=empno
d1["ename"]=ename
d1["salary"]=salary
d1["deptno"]=deptno
pickle.dump(d1,f1)
op=input("enter the option to continue or not")
if op=='n':
break
f1.close()
writebinary()
3)write a python function readdata() to read data from
emp.dat file in the format of
[empno,ename,salary,deptno]
import pickle
def readdata():
f1=open("emp.dat","rb")
try:
while True:
l1=pickle.load(f1)
print(l1)
except EOFError:
f1.close()
readdata()
3)write a python function readdata() to read data from
emp.dat file in the format of
{"empno":empno,"ename":ename,"salary":salary,"deptno":deptno}
solution:
import pickle
def readdata():
f1=open("empdict.dat","rb")
try:
while True:
d1=pickle.load(f1)
print(d1)
except EOFError:
f1.close()
readdata()
"""
{'empno': 1001, 'ename': 'raja', 'salary': 50000, 'deptno': 10}
{'empno': 1002, 'ename': 'kartick', 'salary': 70000, 'deptno': 20}
{'empno': 1003, 'ename': 'saran', 'salary': 30000, 'deptno': 20}
"""
5)Write a python function to read from emp.dat file
and get deptno from user and display the records
in given deptno.
emp.dat str is [empno,ename,salary,deptno]
solution:
import pickle
def searchrecord():
f1=open("emp.dat","rb")
deptno=int(input("enter the search deptno"))
count=0
try:
while True:
l1=pickle.load(f1)
if l1[3]==deptno:
print("found",l1)
count=count+1
except EOFError:
f1.close()
if count==0:
print("deptno is not found")
searchrecord()
5)Write a python function to read from empdict.dat file
and get deptno from user and display the records
in given deptno.
emp.dat str is {"empno":empno,"ename":ename,"salary":salary,
"deptno":deptno}
solution:
import pickle
def searchrecord():
f1=open("empdict.dat","rb")
deptno=int(input("enter the search deptno"))
count=0
try:
while True:
d1=pickle.load(f1)
if d1["deptno"]==deptno:
print("found",d1)
count=count+1
except EOFError:
f1.close()
if count==0:
print("deptno is not found")
searchrecord()
update()
emp.dat file
[1001, 'raja', 60000, 10]
[1002, 'kartick', 90000, 20]
[10003, 'kavin', 78000, 20]
[1004, 'selvi', 20000, 10]
[1005, 'kala', 50000, 20]
7) write a python function to increment the salary 5000
to all employees.
solution:
import pickle
def updaterecord():
f1=open("emp.dat","rb+")
try:
while True:
pos=f1.tell()
l1=pickle.load(f1)
##if condition for particular record
l1[2]=l1[2]+5000
f1.seek(pos)
pickle.dump(l1,f1)
except EOFError:
f1.close()
updaterecord()
def readdata():
f1=open("emp.dat","rb")
try:
while True:
l1=pickle.load(f1)
print(l1)
except EOFError:
f1.close()
readdata()
8)Write apython function to delete a record from emp.dat
file for the given empno.
emp.dat [empno,ename,salary,deptno]
solution:
import pickle
import os
def deleterecord():
f1=open("emp.dat","rb")
f2=open("new.dat","wb")
empno=int(input("enter the empno"))
try:
while True:
l1=pickle.load(f1)
if l1[0]!=empno:
pickle.dump(l1,f2)
except EOFError:
f1.close()
f2.close()
os.remove("emp.dat")
os.rename("new.dat","emp.dat")
deleterecord()
def readdata():
f1=open("emp.dat","rb")
try:
while True:
l1=pickle.load(f1)
print(l1)
except EOFError:
f1.close()
readdata()
Tasks
1. consider the file product.dat containing records of the following
str
[prodid,prodname,price,category]
i)write a function countrec() to count the no of records in
product.dat file.
solution:
def countrec():
f1=open("product.dat","rb")
count=0
try:
while True:
f1=pickle.load(f1)
count=count+1
except EOFError:
f1.close()
print("no of records=",count)
countrec()
Tasks
1. consider the file product.dat containing records of the following
str
[prodid,prodname,price,category]
ii)a)Write a function copydata() that reads contents from
the file product.dat and copies those records category is
'Homeappliances" to another file named as new.dat file.
b)write a function display() to display the content from
new.dat file
pickle.load(f1)
1001 lg 888 home
for record in content
solution:
import pickle
def copydata():
f1=open("product.dat","rb")
f2=open("new.dat","wb")
try:
while True:
l1=pickle.load(f1)
if l1[3]=="Homeappliances":
pickle.dump(l1,f2)
except EOFError:
f1.close()
f2.close()
def displaydata():
f1=open("new.dat","rb")
try:
while True:
l1=pickle.load(f1)
print(l1)
except EOFError:
f1.close()
copydata()
displaydata()
