Controlling Randomness

Python

Random Module

• random.seed(a=None, version=2):

  random.seed(42) # Use an integer seed
  random.seed("hello") # Use a string seed
  random.seed() # Seed from current time or OS sources
  

  • Purpose: Initializes the random number generator. Using the same seed value will produce the same sequence of random numbers. Useful for reproducible results.
  • Parameters:
    • a: The seed value. Can be any hashable object. If None, it seeds from the current time or OS-specific randomness sources.
    • version: Specifies how the seed is converted to an integer. Version 2 is the default and recommended.
  • Returns: None.

• random.getstate():

  current_state = random.getstate()
  

  • Purpose: Returns an object representing the current internal state of the generator. This state can be passed to setstate() to restore the state.
  • Parameters: None.
  • Returns: A tuple containing the internal state.

• random.setstate(state):

  # Assume 'saved_state' holds a state obtained from getstate()
  random.setstate(saved_state)
  

  • Purpose: Restores the internal state of the generator. This allows you to reproduce a sequence of random numbers from a saved point.
  • Parameters:
    • state: The state object obtained from a previous call to getstate().
  • Returns: None.

Making Random Selections (with replacement)

• random.choices(population, weights=None, cum_weights=None, k=1):

  # Select 5 items with replacement
  selection = random.choices([1, 2, 3, 4, 5], k=5)
  
  # Select with weights (e.g., 1 is twice as likely as 2)
  weighted_selection = random.choices(['A', 'B'], weights=[2, 1], k=10)
  

  • Purpose: Returns a list of elements from the population with replacement. Useful when you want to select items multiple times.
  • Parameters:
    • population: A sequence or set to sample from.
    • weights: (Optional) A list of weights corresponding to the population elements.
    • cum_weights: (Optional) A list of cumulative weights. Cannot be used with weights.
    • k: (Optional) The number of elements to choose (default is 1).
  • Returns: A new list containing the selected elements.