python - WindowsError: [Error 32] The process cannot access the file because it is being used by another process: 'new.dat'

Question

the below is my entire program .. i just don't know were am I going wrong it keeps on telling that the process is eing used by some other file ...I just don't understand please help me out as I need to submit this within two days time

import os
import pickle
password=123
l=input("Enter Password :")
if l==password:
    print"--------Welcome Admin--------"
    class new:
        def __init__(self,a,b,c):
            self.acno=a
            self.acna=b
            self.ini=c
        def display(self):
            print self.acno,self.acna,self.ini
    def form(): # creating new account holders
        print"      ---New Account Entry Form---   "
        n=input("Enter the no. Forms")
        f1=open("new.dat","ab")
        for i in range (n):
            a=input("Enter The Account No:")
            b=raw_input("Enter The Name of The Account Holder:")
            c=input("Enter The Initial Amount (>=5000 ):")
            if c<5000:
                print "Initial Amount Too Low"
                c=input("Enter The Initial Amount (>=5000 ):")
            e=new(a,b,c)
            pickle.dump(e,f1)
        f1.close()
        print"--------Account Created Successfully--------------"
    def depo():#depositing amount in the account
        print"  ---- Account Deposition Form ---- "
        p=input("Enter the Account Number:")
        f1=open("new.dat","rb")
        f2=open("dep.dat","wb")
        amt=input("Enter the Amount to Deposit :")
        try:
            while True:
                s=pickle.load(f1)
                if s.acno==p:

                    s.ini+=amt
                    pickle.dump(s,f2)
        except EOFError:
            f1.close()
            f2.close()
        print"Amount Deposited Successfully"
        os.remove("new.dat")
        os.rename("dep.dat","new.dat")
    def withdraw():#to withdraw 
        print "            Account Transaction Form            "
        p=input("enter the account n:")
        f2=open("new.dat","rb")
        f3=open("f2.dat","wb")
        amt=input("Enter the amount to Withdraw:")
        try:
            while True:
                s=pickle.load(f2)
                if s.acno==p:
                    if s.ini>amt or s.ini==amt :
                        s.ini-=amt
                        pickle.dump(s,f3)
                        print "Amount Withdrawed"
                    elif s.ini<amt:
                        print "No sufficient balance "
                    else:
                        print " Account no. invalid"
        except EOFError:
            f2.close()
            f3.close()
        os.remove("new.dat")
        os.rename("f2.dat","new.dat")
    def balance():#check the balance 
        print"          Balance Amount Details"
        p=input("Enter the Account Number:")
        f3=open("new.dat","rb")
        try:
            while True:
                s=pickle.load(f3)
                if s.acno==p:
                    print "the Balance Amount for Acc. no. ",p,"is :", s.ini
        except EOFError:
            f3.close()
    def displa():#display all the account holders 
        print "      All Account Holders List      "
        f1=open("new.dat","rb")
        try :
            while True:
                k=pickle.load(f1)
                k.display()
        except EOFError:
            f1.close()
    def dele(): # to delete the account holder error here
        print "       Account Deletion Form"
        f1=open("new.dat","rb")
        f2=open("tnew.dat","wb")
        try:
            e=pickle.load(f1)
            no=input("Enter the Account No:")
            if e.acno!=no:
                pickle.dump(e,f2)
        except EOFError:
            f2.close()
            f1.close()
        os.remove("new.dat") #error here
        os.rename("tnew.dat","new.dat") # error here
        f1.close()
    while True:
        print"-----------------------------------------------------------------------------------------------------------------"
        print"                                                                               Bank Management System"
        print"                                                                                                       "
        print"---Main Menu--- :"
        print"1. New account"
        print"2. Deposit amount"
        print"3. Withdraw amount"
        print"4. Balance account"
        print"5. All Account Holders List "
        print"6. Close An Account"
        print"7. Exit"
        choice=input("Enter Your Option (1-7):")
        if choice==1:
            form()
        elif choice==2:
            depo()
        elif choice==3:
            withdraw()
        elif choice==4:
            balance()
        elif choice==5:
            displa()
        elif choice==6:
            dele()
        else:
            print "-------Login In Later----------"
            break
else:
    print "PASSWORD Incorrect"

Answer 1

Try to f1=open("new.dat","rb") and then os.remove("new.dat") without closing it first; You cannot delete it and the error occures because the file is under 'another process', in other words it's under reading

You shouldn't ever open the file with f = open(filename, 'x') and then close with f.close(), it might create problems exactly like yours if for some reason the program doesn't execute the closure...

Instead, try to rewrite your functions using with open(filename, 'x') as f:, it automatically closes the file when the code within has finished to run or on error without the program being affected

http://effbot.org/zone/python-with-statement.htm

Otherwise, if you don't want to mess everything up (note that your functions keep the the files open if error doesn't occur), try to change every except EOFError: block with finally:, which, at the end, is the same as using with.

From source:

"The try-finally construct guarantees that the code under the finally part is always executed, even if the code that does the work doesn’t finish."

This should assure the closure