Master Python’s Pickle: Serialize Objects Easily with Real Code Examples

What is the pickle module?

Pickle is a Python-specific persistence module that can serialize various data, including custom classes, making it suitable for storing complex Python objects.

However, the serialized string is not human‑readable and can only be used within Python environments, so it is not suitable for data exchange with other languages.

Purpose of the pickle module

It allows you to save Python objects directly to a file without converting them to strings first, handling the binary format automatically and reducing the amount of code needed for file I/O.

Main methods

1. pickle.dump(obj, file)

Saves a Python object to a file in pickle format.

with open('data.pickle', 'wb') as f:
    pickle.dump(data, f)

Opening the resulting file in a text editor shows unreadable binary data.

Result:

2. pickle.dumps(obj)

Serializes a Python object to a bytes string.

import pickle
dic = {"k1":"v1","k2":123}
s = pickle.dumps(dic)
print(s)

Result:

3. pickle.load(file)

Loads data from a pickle file and converts it back to Python objects.

with open('data.pickle', 'rb') as f:
    data = pickle.load(f)

4. pickle.loads(bytes_object)

Deserializes a bytes string produced by pickle.dumps back into Python objects.

import pickle
dic = {"k1":"v1","k2":123}
s = pickle.dumps(dic)
dic2 = pickle.loads(s)
print(dic2)

Result:

Project demonstration

Example 1

import pickle

with open('data.pickle', 'rb') as f:
    data = pickle.load(f)

The .pickle file appears as garbled text when opened with a plain text editor.

Result:

Example 2

Pickle can serialize custom Python classes, but the class definition must be available when deserializing.

import pickle

class Person:
    def __init__(self, n, a):
        self.name = n
        self.age = a

    def show(self):
        print(self.name + "_" + str(self.age))

aa = Person("张三", 20)
aa.show()
f = open('2.txt', 'wb')
pickle.dump(aa, f)
f.close()
# del Person  # If this line were uncommented, loading would fail
f = open('2.txt', 'rb')
bb = pickle.load(f)
f.close()
bb.show()

Result:

Conclusion

This article introduced Python’s pickle module, detailed its main functions, addressed common issues, and provided practical code examples to help readers understand and apply pickle for object persistence in real projects.