Question

What I have is 3 dictionaries dumping with pickle to 3 different files. I had originally just written a read and write function for each file so a total of 6 functions. So last night I tried to make it so I would only have to use 1 read function and 1 write function. I got the write function to work but the read function is not. I have been looking since last night for a solution to this problem and I am fed up so any help you can give I would appreciate.
I am new to programming/python if you could not tell. Here is the code I’m using:

w = {} # would be past in as source

def writing(filename, source): 
    with open(filename, 'wb') as st:
        pickle.dump(source, st)

def reading(filename, source):
    with open(filename, 'rb') as st:
        source = pickle.loads(st.read())

reading('test.txt', w)

The error I got is:

Traceback (most recent call last):
  File "./database.py", line 303, in <module>
   pw.check_pwd(p)
  File "./database.py", line 47, in check_pwd
    if self.pwds[self.user] == hashlib.sha512(self.pwd + self.salt).hexdigest():
KeyError: 'Codex' this was the error I was getting sorry for the bad post

Answer 1

I do not know what problem you are trying, but I am very confident that you want the result of the unpickling in the global w variable, right? Well, you cannot do it this way: when you attribute a value to the source variable, you are updating only the local variable source but the variable w still points to the same value. Maybe this answer may help you to understand what is happening.

There are various solutions to it. One of my favorite ones is the @katrielatex one: return the value:

def reading(filename, source):
    with open(filename, 'rb') as st:
        source = pickle.loads(st.read())
    return source
w = reading(filename, w)

Actually, you do not even need the source parameter:

def reading(filename):
    with open(filename, 'rb') as st:
        source = pickle.loads(st.read())
        return source

w = reading(filename)

Another solution is to update the dictionary pointed by source. In this case, no return is needed:

def reading(filename, source):
    with open(filename, 'rb') as st:
        source.update(pickle.loads(st.read()))

reading(filename, w)

Also, you can make w a global variable inside the function (but it is the worst solution):

def reading(filename):
    global w
    with open(filename, 'rb') as st:
        w = pickle.loads(st.read())

reading(filename)