Saving and loading multiple objects in pickle file?

user_2837388 0
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I have a class that serves players in a game, creates them and other things.

I need to save these player objects in a file to use it later. I've tried the pickle module but I don't know how to save multiple objects and again loading them? Is there a way to do that or should I use other classes such as lists and save and load my objects in a list?

Is there a better way?

pickle object python-3.x class python
8 Answers

If you're dumping it iteratively, you'd have to read it iteratively as well.

You can run a loop (as the accepted answer shows) to keep unpickling rows until you reach the end-of-file (at which point an EOFError is raised).

data = []
with open("data.pickle", "rb") as f:
    while True:
        try:
            data.append(pickle.load(f))
        except EOFError:
            break

Minimal Verifiable Example

import pickle

# Dumping step
data = [{'a': 1}, {'b': 2}]
with open('test.pkl', 'wb') as f:
    for d in data:
        pickle.dump(d, f)

# Loading step
data2 = []
with open('test.pkl', 'rb') as f:
    while True:
        try:
            data2.append(pickle.load(f))
        except EOFError:
            break

data2
# [{'a': 1}, {'b': 2}]

data == data2
# True

Of course, this is under the assumption that your objects have to be pickled individually. You can also store your data as a single list of object, then use a single pickle/unpickle call (no need for loops).

data = [{'a':1}, {'b':2}]  # list of dicts as an example
with open('test.pkl', 'wb') as f:
    pickle.dump(data, f)

with open('test.pkl', 'rb') as f:
    data2 = pickle.load(f)

data2
# [{'a': 1}, {'b': 2}]
user_49090870

Here is how to dump two (or more dictionaries) using pickle, and extract it back:

import pickle

dict_1 = {1: 'one', 2: 'two'}
dict_2 = {1: {1: 'one'}, 2: {2: 'two'}}

F = open('data_file1.pkl', 'wb')
pickle.dump(dict_1, F)
pickle.dump(dict_2, F)
F.close()

=========================================

import pickle

dict_1 = {1: 'one', 2: 'two'}
dict_2 = {1: {1: 'one'}, 2: {2: 'two'}}

F = open('data_file1.pkl', 'rb')
G = pickle.load(F)
print(G)
H = pickle.load(F)
print(H)
F.close()
user_143204680

Suppose we have saved objects in the file of an Employee class. Here is the code to read all objects, one by one, from file:

 e = Employee()    

with open(filename, 'rb') as a:
    while True:
        try:
            e = pickle.load(a)
            e.ShowRecord()
        except EOFError:
            break
user_10764970
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