51 lines
1.7 KiB
Markdown
51 lines
1.7 KiB
Markdown
|
---
|
||
|
|
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)
|