pickle and Serialization

The pickle module serializes Python objects into bytes for storage or transmission. While convenient for Python-specific data, pickle has security implications and limitations compared to other formats.

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Basic Pickling

Serializing Objects

import pickle

data = {"name": "Alice", "age": 30, "scores": [95, 87, 92]}

pickled = pickle.dumps(data)
print(f"Pickled: {type(pickled)}")

restored = pickle.loads(pickled)
print(restored)

Output:

Pickled: <class 'bytes'>
{'name': 'Alice', 'age': 30, 'scores': [95, 87, 92]}

File Persistence

import pickle
import io

data = [1, 2, 3, 4, 5]
buffer = io.BytesIO()

pickle.dump(data, buffer)

buffer.seek(0)
restored = pickle.load(buffer)
print(restored)

Output:

[1, 2, 3, 4, 5]

Custom Objects

Pickling Classes

import pickle
import io

class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def __repr__(self):
        return f"Dog(name={self.name}, age={self.age})"

dog = Dog("Buddy", 5)
buffer = io.BytesIO()

pickle.dump(dog, buffer)
buffer.seek(0)
restored = pickle.load(buffer)
print(restored)

Output:

Dog(name=Buddy, age=5)

Protocols and Versions

Protocol Versions

import pickle
import io

data = {"key": "value"}

for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
    buffer = io.BytesIO()
    pickle.dump(data, buffer, protocol=protocol)
    size = buffer.tell()
    print(f"Protocol {protocol}: {size} bytes")

Output:

Protocol 0: 27 bytes
Protocol 1: 17 bytes
Protocol 2: 17 bytes
Protocol 3: 16 bytes
Protocol 4: 15 bytes
Protocol 5: 10 bytes

Security Considerations

Pickle Security Warning

import pickle
import json

data = {"name": "Alice", "age": 30}
safe_json = json.dumps(data)
restored = json.loads(safe_json)
print(restored)

Output:

{'name': 'Alice', 'age': 30}