Apply a condition only once in a recursion-CodePudding

I want to apply a condition inside a resursion only once. My data structure looks as follows

stages = {"stage_1": False, "stage_2":False, "stage_3":False,"state_4": False}

I want to pick any stage randomly from it and change the status to True. But when total number of true stage is 3 I want to randomly change a True stage to False. But only once. Then it should continue to turn stages in to True. When all 4 stages are true. The recursion process stops. How can I do that ? I have tried the following code. but it is not complete.

def process(stages):
    all_stages = [stage for stage, status in stages.items() if status == False]
    if len(all_stages) !=0:
        print(all_stages)
        select_ = random.choice(all_stages)
        print("\tselected stage: ",select_)
        
        stages[select_] = True
        process(stages)
    else:
        print("Done")
        print(stages)

process(stages)

This works without adding that extra condition. I have tried the following one. But that does not work

def process(stages):
    all_stages = [stage for stage, status in stages.items() if status == False]
    if len(all_stages) !=0:
        print(all_stages)
        select_ = random.choice(all_stages)
        print("\tselected stage: ",select_)
        
        stages[select_] = True

        if len(all_stages) == 1:
            select_ = random.choice([stage for stage, status in stages.items() if status == True])
            stages[select_] = False
        process(stages)
    else:
        print("Done")
        print(stages)

process(stages)

CodePudding user response：

As with many recursion problems, adding a state to your function call will help you a lot.

Consider making an inner call to process_internal() that would get the current state of the recursion, whether it's stage 0 (False -> True), stage 1 (True -> False) or stage 2 (False -> True).

import random

def flip_random_state(stages, relevant_bool_val):
    relevant_stages = [stage for stage, status in stages.items() if status == relevant_bool_val]
    print(relevant_stages)
    selected_stage = random.choice(relevant_stages)
    print(f"\tSelected stage: {selected_stage}")
    stages[selected_stage] = not stages[selected_stage]
    return stages

def count_stages_with_status(stages, input_status):
    return len([stage for stage, status in stages.items() if status == input_status])

def process_internal(stages, state):
    if state == 2 and count_stages_with_status(stages, True) == 4:
        print("Done")
        print(stages)
        return
    
    if state == 0 or state == 2:
        relevant_bool_val = False
    else:
        relevant_bool_val = True

    if state == 1 and count_stages_with_status(stages, False) == 0:
        state = 2
    
    if state == 0 and count_stages_with_status(stages, True) == 3:
        state = 1

    stages = flip_random_state(stages, relevant_bool_val)

    process_internal(stages, state)

def process(stages):
    return process_internal(stages, 0)

stages = {"stage_1": False, "stage_2": False, "stage_3": False,"state_4": False}
process(stages)

CodePudding user response：

You could add a global variable as a flag to get, wheather you already set one back to False, or add an optional parameter like returnedToFalse=False And set it to true when you eventually set one to false already.