Python

JSON Serialization for Custom Classes

Attempting to run json.dumps() on a custom class results in the error: "Object of type ____ is not JSON serializable." By returning the __dict__ as the serializer in a lambda passed to the default parameter of json.dumps(), we can get the class to serialize to JSON.

import json

class Object:
    def __str__(self):
        return json.dumps(
            self,
            default=lambda o: o.__dict__, 
            sort_keys=True,
            indent=2)    
    def __repr__(self):
        self.__str__()


# Even better
from dataclasses import dataclass
import orjson

@dataclass()
class Car:
  def __init__(self):
    self.wheel_count = 4

c1 = Car()

print( orjson.dumps(c1).decode('utf-8') )  # Returns {"wheel_count":4}
	  

Converting Nested Loops to Single with Cartesian Product

$ python3
Python 3.12.3 (main, May 22 2024, 17:31:33) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

>>> arr1 = [1, 2, 3]
>>> arr2 = [2, 3, 5]
>>> for x in arr1:
...   for y in arr2:
...     if x == y:
...       print(str(x) + ' is in both arrays')
...
2 is in both arrays
3 is in both arrays


>>> from itertools import product
>>> arr1 = [1, 2, 3]
>>> arr2 = [2, 3, 5]
>>> for x, y in list(product(arr1, arr2)):
...     if x == y:
...       print(str(x) + ' is in both arrays')
...
2 is in both arrays
3 is in both arrays
    

String Interpolation

$ python3
Python 3.12.3 (main, May 22 2024, 17:31:33) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

>>> name = "Nitin"
>>> age = 40

>>> 'Name: %s ; Age: %d' % (name, age)
'Name: Nitin ; Age: 40'

>>> f'Name: {name} ; Age: {age}'
'Name: Nitin ; Age: 40'

>>> 'Name: %{name}s ; Age: %{age}d' % {'name': name, 'age': age}
'Name: Nitin ; Age: 40'

>>> 'Name: {name} ; Age: {age}'.format(name=name, age=age)
'Name: Nitin ; Age: 40'

>>> from string import Template
>>> tpl = Template('Name: $name ; Age: $age')
>>> tpl.substitute(name=name, age=age)
'Name: Nitin ; Age: 40'