1st August 2022

Coding⚑

Python⚑

Python Snippets⚑

• New: Initialize a dataclass with kwargs.

  If you care about accessing attributes by name, or if you can't distinguish between known and unknown arguments during initialisation, then your last resort without rewriting __init__ (which pretty much defeats the purpose of using dataclasses in the first place) is writing a @classmethod:

  from dataclasses import dataclass
  from inspect import signature
  
  @dataclass
  class Container:
      user_id: int
      body: str
  
      @classmethod
      def from_kwargs(cls, **kwargs):
          # fetch the constructor's signature
          cls_fields = {field for field in signature(cls).parameters}
  
          # split the kwargs into native ones and new ones
          native_args, new_args = {}, {}
          for key, value in kwargs.items():
              if key in cls_fields:
                  native_args[key] = value
              else:
                  new_args[key] = value
  
          # use the native ones to create the class ...
          ret = cls(**native_args)
  
          # ... and add the new ones by hand
          for new_key, new_value in new_args.items():
              setattr(ret, new_key, new_value)
          return ret
  

  Usage:

  params = {'user_id': 1, 'body': 'foo', 'bar': 'baz', 'amount': 10}
  Container(**params)  # still doesn't work, raises a TypeError
  c = Container.from_kwargs(**params)
  print(c.bar)  # prints: 'baz'
  

• New: Replace a substring of a string.

  txt = "I like bananas"
  
  x = txt.replace("bananas", "apples")
  

Operating Systems⚑

Linux⚑

Linux Snippets⚑

• New: Scan a physical page in Linux.

  Install xsane and run it.

Pipx⚑

• New: Introduce pipx.

  Pipx is a command line tool to install and run Python applications in isolated environments.

  Very useful not to pollute your user or device python environments.

  Install it with:

  bash pip install pipx