Problem 5.71 - Thermal Deformation

Picture with a weightless bar supported on two posts. The left post is made of PVC with a height h and the right post is made of Polycarbonate with a height h. The bar is length L. [Problem adapted from © Kurt Gramoll CC BY NC-SA 4.0]

#| standalone: true
#| viewerHeight: 600
#| components: [viewer]

from shiny import App, render, ui, reactive
import random
import asyncio
import io
import math
import string
from datetime import datetime
from pathlib import Path
from math import atan, degrees

def generate_random_letters(length):
    # Generate a random string of letters of specified length
    return ''.join(random.choice(string.ascii_lowercase) for _ in range(length))

problem_ID="243"
L=reactive.Value("__")
h=reactive.Value("__")
delT=reactive.Value("__")
apoly=reactive.Value("__")
apvc=reactive.Value("__")

attempts=["Timestamp,Attempt,Answer,Feedback\n"]

app_ui = ui.page_fluid(
    ui.markdown("**Please enter your ID number from your instructor and click to generate your problem**"),
    ui.input_text("ID","", placeholder="Enter ID Number Here"),
    ui.input_action_button("generate_problem", "Generate Problem", class_="btn-primary"),
    ui.markdown("**Problem Statement**"),
    ui.output_ui("ui_problem_statement"),
    ui.input_text("answer","Your Answer in units of °", placeholder="Please enter your answer"),
    ui.input_action_button("submit", "Submit Answer", class_="btn-primary"),
    ui.download_button("download", "Download File to Submit", class_="btn-success"),
)

def server(input, output, session):
    # Initialize a counter for attempts
    attempt_counter = reactive.Value(0)

    @output
    @render.ui
    def ui_problem_statement():
        return[ui.markdown(f"A rigid bar is supported by two posts made from PVC and polycarbonate, where length L = {L()} mm and height h = {h()} mm. The temperature of each post is raised by ΔT = {delT()}°C. Determine the angle of the bar with the ground. Assume α<sub>poly</sub> = {apoly()} x 10<sup>-6</sup> /°C and α<sub>PVC</sub> = {apvc()} x 10<sup>-6</sup> /°C.")]
    
    @reactive.Effect
    @reactive.event(input.generate_problem)
    def randomize_vars():
        random.seed(input.ID())
        L.set(random.randrange(50,100,1))
        h.set(L()+random.randrange(15,40,1))
        delT.set(random.randrange(50,100,1))
        apoly.set(random.randrange(6,10,1)/10)
        apvc.set(random.randrange(40,60,1))
        
    @reactive.Effect
    @reactive.event(input.submit)
    def _():
        attempt_counter.set(attempt_counter() + 1)  # Increment the attempt counter on each submission.
        delpvc = apvc()*10**-6*delT()*L()
        delpoly = apoly()*10**-6*delT()*L()
        height = delpvc-delpoly
        instr = degrees(atan(height/L())) 
        if math.isclose(float(input.answer()), instr, rel_tol=0.01):
            check = "*Correct*"
            correct_indicator = "JL"
        else:
            check = "*Not Correct*"
            correct_indicator = "JG"

        # Generate random parts for the encoded attempt.
        random_start = generate_random_letters(4)
        random_middle = generate_random_letters(4)
        random_end = generate_random_letters(4)
        encoded_attempt = f"{random_start}{problem_ID}-{random_middle}{attempt_counter()}{correct_indicator}-{random_end}{input.ID()}"

        # Store the most recent encoded attempt in a reactive value so it persists across submissions
        session.encoded_attempt = reactive.Value(encoded_attempt)

        # Append the attempt data to the attempts list without the encoded attempt
        attempts.append(f"{datetime.now()}, {attempt_counter()}, {input.answer()}, {check}\n")

        # Show feedback to the user.
        feedback = ui.markdown(f"Your answer of {input.answer()} is {check}. For reference in debugging this, the calculated instructor answer is {instr}")
        m = ui.modal(
            feedback,
            title="Feedback",
            easy_close=True
        )
        ui.modal_show(m)

    @session.download(filename=lambda: f"Problem_Log-{problem_ID}-{input.ID()}.csv")
    async def download():
        # Start the CSV with the encoded attempt (without label)
        final_encoded = session.encoded_attempt() if session.encoded_attempt is not None else "No attempts"
        yield f"{final_encoded}\n\n"
        
        # Write the header for the remaining CSV data once
        yield "Timestamp,Attempt,Answer,Feedback\n"
        
        # Write the attempts data, ensure that the header from the attempts list is not written again
        for attempt in attempts[1:]:  # Skip the first element which is the header
            await asyncio.sleep(0.25)  # This delay may not be necessary; adjust as needed
            yield attempt

# App installation
app = App(app_ui, server)