Python - rulebook

Fortunately or not, python is unavoidable. So we need some rules to keep ourselves sane while using it.

XDG and home dir

First, let’s remove the clutter:

• Create startup.py file at "$XDG_CONFIG_HOME"/python/ and add the following code:

  import atexit
  import os
  import readline
  
  histfile = ""
  cachedir = os.getenv("XDG_CACHE_HOME")
  if cachedir == "":
      cachedir = os.path.expanduser("~") 
      histfile = os.path.join(cachedir, "history")
  else:
      histfile = os.path.join(cachedir,"python","history")
  
  hist_len = 0
  
  try:
      readline.read_history_file(histfile)
      hist_len = readline.get_current_history_length()
  except FileNotFoundError:
      open(histfile, 'wb').close()
  
  def save(prev_hist_len, histfile):
      new_hist_len = readline.get_current_history_length()
      readline.set_history_length(-1)
      readline.append_history_file(new_hist_len - prev_hist_len, histfile)
  
  atexit.register(save, hist_len, histfile)
  

• Add (or export) PYTHONSTARTUP variable, i.e. export PYTHONSTARTUP="$XDG_CONFIG_HOME"/python/startup.py
• Create history file at "$XDG_CACHE_HOME"/python/
• Reload the environment (logout should work)

Virtual environments

You must use virtual environments for all your python development. It is not optional.

$ python -m venv env
$ source env/bin/activate.fish # depending on the shell of choice
$ pip install number # e.g.
$ pip freeze > requirements.txt # to list all dependencies and their version into a file
$ pip install -r requirements.txt # to install all required dependencies