Dear ms All.

My name is Adnan , I’m from Sarajevo. I’m new on the Streamlit forum and trying hard to learn Streamlit.

I have one problem with my code that I try to finish. I’ve tried to make some variables which I’ll use to make an formula (objective function) in Pulp. Variables are made using an foor loop and inserted in the list (using selected_rows.iterrow) named decision_variables.

After that I’ve tried to make an objective function which would be product of elements from decision_variables and elements from column ‘Lat’ from table as in the code bellow.

Everything works fine if I choose rows in the right order (first 0. row, then 1., 2. and etc). But if I choose rows randomly (for example 2., then 5., 8. etc) then I got these errors:

“TypeError: Can only add LpConstraintVar, LpConstraint, LpAffineExpression or True objects”

and at the end, after choose randomly rows I’ve got just one product (last choosed, not all products of Lat and decision_variable elements).

What could be a problem?

Here is a code:

import streamlit as st

import pandas as pd

from pulp import *

# Load some example data.

DATA_URL =

“http://s3-us-west-2.amazonaws.com/streamlit-demo-data/uber-raw-data-sep14.csv.gz”

data = st.cache(pd.read_csv)(DATA_URL, nrows=1000)

# Select some rows using st.multiselect.

st.write(‘### Full Dataset’, data)

selected_indices = st.multiselect(‘Select rows:’, data.index)

selected_rows = data.loc[selected_indices]

st.write(‘### Selected Rows’, selected_rows)

decision_variables =

for rownum, row in selected_rows.iterrows():

variable = str(‘x’ + str(rownum))

variable = LpVariable(str(variable), lowBound = 0, upBound = 1, cat= ‘Integer’)

decision_variables.append(variable)

print ("Total_number_of_decision_variables: " + str(len(decision_variables)))

print(decision_variables)

st.write(decision_variables)

# define the problem

prob = LpProblem(‘test’,LpMinimize)

total_cost = “”

for rownum, row in selected_rows.iterrows():

for i, schedule in enumerate(decision_variables):

if rownum == i:

formula = row[‘Lat’]*schedule

total_cost += formula

```
prob += total_cost
```

print ("Optimization function: " + str(total_cost))

st.write(“**Objective function is :**”)

st.title(total_cost)