51 lines
1.7 KiB
Markdown
51 lines
1.7 KiB
Markdown
---
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title: Pickling in Python
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---
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<!-- ### TODO: More on pickle functions (like `pickle.dumps`). -->
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## Overview
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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.
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## Usage Example
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First let's create a class:
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```python
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class ExampleClass():
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def __init__(self, integer, string, number_list):
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self.integer = integer
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self.string = string
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self.number_list = number_list
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def print_attributes(self):
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print(self.integer, self.string, self.number_list)
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def print_sum(self):
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print(sum(self.number_list))
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instance = ExampleClass(10, 'rubberducky', [1, 2, 3, 1, 2])
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instance.print_attributes() # Prints 10 rubberducky [1, 2, 3, 1, 2]
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instance.print_sum() # Prints 9
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````
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Now, let's try pickling it:
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```python
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import pickle
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with open('file.pickle', 'wb') as file:
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pickle.dump(instance, file)
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```
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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:
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```python
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import pickle
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with open('file.pickle', 'rb') as file:
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loaded = pickle.load(file)
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loaded.print_attributes() # Prints 10 rubberducky [1, 2, 3, 1, 2]
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loaded.print_sum() # Prints 9
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```
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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.
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#### More Information
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[Python - Pickling](https://docs.python.org/3/library/pickle.html)
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