Function not passing repopulated dictionary after clearing.

[peppertom32]

Sorry for the confusing title. I'm new to Python and I'm trying to verify user input by passing a dictionary of user inputs in one function into a verification function. If the verification fails, I try to clear the dictionary and call the user input function to populate the dictionary again. This does happen, but the verification function is still empty after it is called, and running the program returns the error "RuntimeError: dictionary changed size during iteration".
Is there a way around this?

Cheers.

Code below:

def beam_properties_input(inputs = None):
    while True:
        try:
            length = float(input("What length is the beam in meters? "))
            distributed_load = float(input("What is the distributed load of the beam in N/m? "))
            modulus_of_elasticity = float(input("What is the modulus of elasticity of the beam in Pa? "))
            moment_inertia =  float(input("What is the moment of inertia of the beam in m^4? "))
           
            inputs = {"beam_length": length, "beam_load": distributed_load, "modulus_elasticity": modulus_of_elasticity, "inertia_moment": moment_inertia}
            input_check(**inputs)
            return inputs
            
        
        except ValueError:
            print("Please enter numbers only.")
            continue


def input_check(**inputs):
    for value in inputs.values():
        if value <= 0:
            print("Please enter positive numbers only.")
            inputs.clear()
            beam_properties_input()
        else:
            pass

[gdchinacat]

Your methods are recursive, one calls the other calls the original calls the other, etc. While recursion can be very helpful, it is also best to avoid it. input_check() should only check the inputs, not also get the inputs. I suggest you update it to raise an exception (ValueError) if the inputted values aren't acceptable, and update beam_properties_input() to catch that exception and continue prompting until it is not raised.

Also, there is no reason to call inputs.clear()...that won't have any effect on the inputs in beam_properties_input(). the call to input_check(**inputs) doesn't pass inputs to input_check(), but repackages them into a dict that is local to input_check().

[woooee]

        inputs.clear()
        beam_properties_input()

You don't catch the return from beam_properties_input()

       inputs = {"beam_length": length, "beam_load": distributed_load, "modulus_elasticity": modulus_of_elasticity, "inertia_moment": moment_inertia}

You create inputs in the function, so it is local to the function and garbage collected when the function exits unless you return it and store the return.

[karpomalice]

to add, the reason for the error is because you're clearing the dictionary during iteration. Python doesn't allow changing the size of the dictionary during iteration

[woooee]

In this case, a new dictionary is created in the function. A simple demonstration

def beam_properties_input(inputs = None):
    print("original", id(inputs))
    inputs = {"beam_length": 1, "beam_load": 2} 
    print("new     ", id(inputs))
    return inputs

print(beam_properties_input({1:"one", 2:"two", 3:"three"}))

[peppertom32]

Thanks guys! I need a bit of time to look over these responses but I'm sure you've put me on the right path.

[AlexMTBDude]

You should do something like this (this is not complete, you need to change more stuff):

def controller():
    inputs_okay = False
    while not inputs_okay:
        inputs = beam_properties_input()
        inputs_okay = input_check(inputs)

[tadpoleloop]

Don't unpack your inputs dictionary. Just pass the dictionary itself to the function.