Using cPickle

[MRAB]

mmcclaf wrote:
> On Feb 6, 10:25 am, Steve Holden <st... at holdenweb.com> wrote:
>> mmcclaf wrote:
>>> Hi there,
>>> I have to make a small database using cPickle. I'm having troubles
>>> trying to read in the information if it's more than one line. I'm
>>> pretty sure it's in the line "for line in stuff:" Can anyone help me
>>> out? Basically the end result is wanting it to look something like
>>> what is down below when list is typed in:
>>> Last name                 First Name                Email Address
>>> Doe                          John
>>> j... at doe.com
>>> [code]
>>> # @author: Ocdt Murray McClafferty 24656
>>> # This will manage a small database using the cPickle module.
>>> # It must maintain a list of last names, first names and email
>>> addresses, and must let a user interact with the program
>>> #
>>> #!usr/bin/python
>>> # -*- coding: utf-8 -*-
>>> import sys
>>> import cPickle
>>> #
>>> format = '%s             %s                  %s'
>>> try:
>>>    filename = sys.argv[1]
>>>    input = open(filename, 'r')
>>> except IOError:
>>>    print 'File is not available, will create a new file now'
>>>    lastName='Last Name'
>>>    firstName='First Name'
>>>    email= 'Email'
>>>    #input.close()
>>>    output=open (filename, 'w')
>>>    total = format%(lastName, firstName, email)
>>>    cPickle.dump(total,output)
>>>    #cPickle.dump(firstName,output)
>>>    #cPickle.dump(email,output)
>>>    output.close()
>>> except EOFError:
>>>    print 'File is empty'
>>> #datas = cPickle.load(input)
>>> while True:
>>>    command=sys.stdin.readline()[:-1]
>>>    if command=='list': #lists the data in the file
>>>            input = open(filename, 'r')
>>>            stuff=cPickle.load(input)
>>>            for line in stuff:
>>>                    #firstName=cPickle.load(input)
>>>                    #email=cPickle.load(input)
>>>                    #print repr (lastName).rjust(10), repr(firstName).rjust(20), repr
>>> (email).rjust(20)
>>>                    stuff=cPickle.load(input)
>>>                    print stuff
>>>                    print line
>>>            input.close()
>>>    if command=='exit' or command=='quit' : #NEVER forget the exit!!!
>>>            print 'Save changes? y for Yes, n for No'
>>>            commandSave=sys.stdin.readline()[:-1]
>>>            if commandSave =='y': #if the user wants to save
>>>                    output=open(filename, 'w')
>>>                    cPickle.dump(work,output)
>>>                    output.close()
>>>                    sys.exit(0)
>>>            if commandSave =='n': #no save
>>>                    input.close()
>>>                    sys.exit(0)
>>>    if command=='add': #adds an entity to the file
>>>            print 'Last name?'
>>>            lastName=sys.stdin.readline()[:-1]
>>>            print 'First name?'
>>>            firstName=sys.stdin.readline()[:-1]
>>>            print 'Email address?'
>>>            email=sys.stdin.readline()[:-1]
>>>            work = format%(lastName, firstName, email)
>>>            #output=open(filename, 'w')
>>>            #data=cPickle.load(output)
>>>            #data.append(work)
>>>            #output.close()
>>>            output=open(filename, 'a')
>>>            cPickle.dump(work,output)
>>>            output.close()
>>> [/code]
>>> All help would be appreciated. I am new to Python and this seems to be
>>> quite a challenge for me.
>> Make sure you use modes "rb" and "wb" when you open the pickle files. If
>> you are running on Windows this can make a difference.
>>
>> regards
>>  Steve
>> --
>> Steve Holden        +1 571 484 6266   +1 800 494 3119
>> Holden Web LLC              http://www.holdenweb.com/
> 
> I've tried both rb and wb as well as r and w, there appears to be no
> difference in the running of the code.
> 
"cPickle.dump(work,output)" writes a string and 
"stuff=cPickle.load(input)" just reads that string, so "for line in 
stuff:" is iterating through the characters if the string. You need to 
use cPickle.load() to read each string (line).