Building a calculator

Hello, 

I am new to Django and trying to learn using the framework as best as i can.

I am trying to build an application that can calculate thickness for a vessel under two cases: internal or external pressure. 

I am really stuck trying to answer the following (Please Help):

1) How can i redirect the user to one of the two calculation pages (where they will need to enter values in a field and see the result on the same page) based on their choice from ModelChoiceField?

2) How to do the calculations based on the equations i have and the iterations they require ( i know i should write them in the views but not sure how exactly)?

Please, if there is any other problem or you require further details on what i am trying to achieve, do tell me.

Thanks a lot!

- The calculations i am trying to do through the web app ( for the case of the external pressure)

p = float(input("Enter pressure in Kpa "))

if (p < 20684): # p < 3000 psi

    

  e = float(input("Enter joint efficiency "))

  c = float(input("Enter corrosion allowance in mm "))

  ltt = float(input("Enter tan-tan length in mm "))

  do = float(input("Enter outside diameter in mm "))

  t= float(input("Initialize thickness value in mm "))

  step_size= float(input("Enter step side in mm "))

  

else: 

      print("pressure too high!")

      quit()

  

print("Select Material.")

print("1.ASME SA285 C")

print("2.ASME SA516")

print("3.ASME SA537")

print("4.Enter Material")

choice = input("Enter choice(1/2/3):")

#s=allowable stress

if choice == '1':

    s=235000 

    el=206842718.79

   

    

if choice == '2':

    s=260000 

    el=2

    

    

if choice == '3':

    s=310000 

    el=3

   

    

if choice == '4':

    s=int(input("Enter material allowable stress in Kpa "))

    el=int(input("Enter modulus of elasticity in Kpa "))

    

allowable_pressure=0

while allowable_pressure < p:

    t=t+step_size

    

    d=do-2*t

    

    print("Select Head type.")

    print("1.hemi-heads")

    print("2.2:1 S.E. heads")

    print("3.100% - 6% heads")

    choice_1 = input("Enter choice(1/2/3):")

    if choice_1 == '1':

      l=ltt + 0.333*d

    

    if choice_1 == '2':

      l=ltt+0.16666*d

    

    if choice_1 == '3':

      l=ltt+0.16666*d

      

    #will work on digitizing the graphs to avoid having the user input values at every iteration

    print("your L/Do is ", l/do, "your Do/t is ", do/t)

    print("determine Factor A from ASME Code, Section II, Part D, Subpart 3, Fig G: Geometric Chart for Components Under External or Compressive Loadings")

    a = float(input("Enter A"))

    print("Using Factor "A", enter the applicable material chart from ASME Code, Section II, Part D, Subpart 3 at the appropriate temperature and determine Factor "B."")

    b = float(input("Enter B"))

    print("if A is to the left of material graph enter (1), on(2)")

    choice_2 = input("Enter choice(1/2):")  

      

    if choice_2 == '1':

       allowable_pressure=(3*do/t)

    

    if choice_2 == '2':

       allowable_pressure=(4*a*el)/(3*do/t)

    

print (t, "mm")

print (allowable_pressure, "Kpa")  

    

- Views.py

from django.shortcuts import render, redirect

from django.contrib.auth.decorators import login_required

from .import forms

@login_required(login_url="/login/")

def AddMaterial(request):

    form=forms.AddMaterial()

    return render(request, 'webapp/Add_Material.html',{'form':form})

def thickness_l(p,ri,s,e,c):

   return (p*ri)/((2*s*e)+(0.4*p))+c

def thickness_c(p,ri,s,e,c):

   return (p*ri)/((2*s*e)-(0.6*p))+c

def thickness(p,ri,s,e,c):

    if thickness_l(p,ri,s,e,c) < thickness_c(p,ri,s,e,c):

         return thickness_c(p,ri,s,e,c)

    else:

         return thickness_l(p,ri,s,e,c)

# add equations for external pressure

@login_required(login_url="/login/")

def selection(request, ):

    if request.method == 'POST':

        form=forms.Pressure_choice(request.POST)

        #if choice = internal

        if form = #?

            return redirect('/Internal/')

        #if choice = external

        elif form = #?

            return redirect('/External/')

    else

        return render(request, 'webapp/selection.html',{'form':form})

        

@login_required(login_url="/login/")

def Internal_Pressure(request):

    form=forms.Internal_Pressure()

    return render(request, 'webapp/Internal_Pressure.html',{'form':form})

@login_required(login_url="/login/")

def External_Pressure(request):

    form=forms.External_Pressure()

    return render(request, 'webapp/External_Pressure.html',{'form':form})

- forms.py

from django import forms

from .import models

class AddMaterial(forms.ModelForm):

    class Meta:

        model=models.Material

        fields='__all__'

class Pressure_choice(forms.Form):

        CHOICES = (('1', 'Internal Pressure',), ('2', 'External Pressure',))

        choice_field = forms.ChoiceField(widget=forms.RadioSelect, choices=CHOICES)

class Internal_Pressure(forms.Form):

    class Meta:

        Material=models.Material

        Material_choice = forms.ModelChoiceField(queryset=Material.objects.all(), widget=forms.Select)

        Pressure = forms.FloatField()

        Internal_radius = forms.FloatField()

        Joint_efficiency= forms.FloatField()

class External_Pressure(forms.Form):

    class Meta:

        Material=models.Material

        Head=models.Head

        Material_choice = forms.ModelChoiceField(queryset=Material.objects.all(), widget=forms.Select)

        Head_choice=forms.ModelChoiceField(queryset=Head.objects.all(), widget=forms.Select)

        Pressure = forms.FloatField()

        Internal_radius = forms.FloatField()

        Tan_to_Tan_Length= forms.FloatField()

        #etc..

- External_Pressure.html

{% extends 'webapp/base_layout.html' %}

{% block content %}

  <h1>External Pressure</h1>

  <form class="site-form" action="index.html" method="post">

    {%csrf_token%}

    {{ form }}

    <input type="Submit" value="Submit">

{% endblock %}

- urls.py

from django.conf.urls import url

from . import views

from django.contrib.auth.views import login, logout

from django.contrib.staticfiles.urls import staticfiles_urlpatterns

from django.conf.urls.static import static

from django.conf import settings

from django.views.generic.base import RedirectView

urlpatterns = [

    url(r'^$', login, {'template_name': 'registration/login.html'}, name='login'),

    url(r'^logout/$', logout, {'template_name': 'registration/logout.html'}, name='logout'),

    url(r'^Internal/$', views.Internal_Pressure, name='Internal'),

    url(r'^External/$', views.External_Pressure, name='External'),

    url(r'^selection/$', views.selection, name='selection'),

    url(r'^AddMaterial/$', views.AddMaterial, name='AddMaterial'),

    #url(r'^.*$', RedirectView.as_view(pattern_name='login', permanent=False)),

]

urlpatterns += staticfiles_urlpatterns()

urlpatterns += static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)

- models.py

from django.db import models

from django.forms import ModelForm

from django import forms

# Create your models here.

class Material(models.Model):

    Name = models.CharField(max_length=20)

    allow_stress = models.FloatField()

    elasticity = models.FloatField()

    def __str__(self):

        return self.Name

class Head(models.Model):

    Name = models.CharField(max_length=20)

    def __str__(self):

        return self.Name

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