title: My python code is appending and not overwriting. How can I overwrite?
body: <p>Here is my python code:-</p>
  
  <pre><code>f= open("Passes.py", "a+")
  m=open("money.py","r+")
  passes= {}
  init={}
  initial=0
  import time
  print "Welcome to the virtual banking system"
  time.sleep(0.5)
  user=raw_input("Would you like to create a new account? 'Y/N'").lower()
  if user== "y":
    new_user= raw_input("Create a username:")
    new_pass= raw_input("Create a password:")
    p= passes[new_user]= new_user + ":" + new_pass
    f.write(str(p+ "\n"))
    ask=raw_input("Would you like to sign into your account? 'Y/N'").lower()
    if ask=="y":
      user_in=raw_input("Enter your username:")
      if user_in==new_user:
        pass_in=raw_input("Enter your password:")
        if pass_in==new_pass:
          print "Welcome to your account" + " " + new_user
          useropt=raw_input("Would you like to view your balance- enter 1, deposit money- enter 2, withdraw money- enter 3 or exit- enter 4:")
          if useropt=="1":
            print "Your balance is:", initial
          if useropt=="2":
            amountdep= int(raw_input("How much money would you like to deposit?:"))
            initial+=amountdep
            print "Thanks. Your new balance is:", initial
          if useropt=="3":
            amountwith=int(raw_input("How much would you like to withdraw?:"))
            initial-=amountwith
            print "Your balance is:", initial
          i=init[new_user]=str(initial)
          m.write(str(i)+"\n")
      else:
        print "Password not valid"
  
    else:
      print "Username does not exist"
  else:
    user2=raw_input("Do you have an existing account? 'Y/N'").lower()
    if user2=="y":
      existing_user=raw_input("Enter your username:")
      exisitng_pass=raw_input("Enter your password:")
      for passwords in f:
        if passwords==existing_user+":"+exisitng_pass:
          print "Welcome to your account" + " " + existing_user
          useropt2=raw_input("Would you like to view your balance- enter 1, deposit money- enter 2, withdraw money- enter 3 or exit- enter 4:")
          if useropt2=="1":
            for info in m:
              print "Your balance is:", info
          if useropt2=="2":
            amountdep= int(raw_input("How much money would you like to deposit?:"))
            for info in m:
              a=int(info)+int(amountdep)
              print "Your new balance is:", int(a)
              m.write(str(a))
          if useropt2=="3":
            amountwith=int(raw_input("How much would you like to withdraw?:"))
            for info in m:
              t=int(info)-int(amountwith)
              print "Your balance is:", t
              m.write(str(t))
  </code></pre>
  
  <p>Under the last two if statements, when the new amount is written to the file(m.write), it appends to the file, whereas I would like to overwrite it not append it. How can I do this? I have opened the file as "r+". </p>