---
title: Pickling in Python
---

<!-- ### TODO: More on pickle functions (like `pickle.dumps`). -->
## Overview
Pickling refers to the serialization and deserialization of an object in Python. It essentially stores an object to a file so the user can load it later on. During pickling, the Python object is converted to a binary stream.

## Usage Example
First let's create a class:

```python
class ExampleClass():
  def __init__(self, integer, string, number_list):
    self.integer = integer
    self.string = string
    self.number_list = number_list
  def print_attributes(self):
    print(self.integer, self.string, self.number_list)
  def print_sum(self):
    print(sum(self.number_list))

instance = ExampleClass(10, 'rubberducky', [1, 2, 3, 1, 2])
instance.print_attributes() # Prints 10 rubberducky [1, 2, 3, 1, 2]
instance.print_sum() # Prints 9
````
    
Now, let's try pickling it:

```python
import pickle
with open('file.pickle', 'wb') as file:
  pickle.dump(instance, file)
```

This creates the file `file.pickle`. According to [this StackOverflow thread](https://stackoverflow.com/questions/40433474/preferred-or-most-common-file-extension-for-pickle-files), Python 3's preferred extension is `.pickle`. Now we simply need to lead it:

```python
import pickle
with open('file.pickle', 'rb') as file:
  loaded = pickle.load(file)
  loaded.print_attributes() # Prints 10 rubberducky [1, 2, 3, 1, 2]
  loaded.print_sum() # Prints 9
```

It works! Note that both times, `open()`'s mode was `rb` or `wb`, as opposed to the regular `r` or `w` (which stand for read and write). This is because of how pickle works: it uses binary.

#### More Information

[Python - Pickling](https://docs.python.org/3/library/pickle.html)