tkinter entry fields not updating using .insert

Question

I'm trying to create a GUI and I am having trouble getting read only entry fields to insert a value. I've tried using a text value and this didn't insert anything into the field.

here is the function:

def calculateFinalCMD():

    global planetInfo
    global getDestinationNum

    displayfc1.grid(row=14, column=2)
    displayfc1.insert(0, ((100 - int(crewInfo[0][1])) * planetInfo[getDestinationNum][1]))
    displayfc2.grid(row=15, column=2)
    displayfc2.insert(0, ((100 - int(crewInfo[1][1])) * planetInfo[getDestinationNum][1]))
    displayfc3.grid(row=16, column=2)
    displayfc3.insert(0, ((100 - int(crewInfo[2][1])) * planetInfo[getDestinationNum][1]))
    displayfc4.grid(row=17, column=2)
    displayfc4.insert(0, ((100 - int(crewInfo[3][1])) * planetInfo[getDestinationNum][1]))
    displayms1.grid(row=18, column=2)
    displayms1.insert(0, ((150 - int(crewInfo[4][1])) * planetInfo[getDestinationNum][1]))
    displayms2.grid(row=19, column=2)
    displayms2.insert(0, ((150 - int(crewInfo[5][1])) * planetInfo[getDestinationNum][1]))

Here are the entry fields which are separate from the function, getDestinationNum is updated by another entry field earlier in the code.

getDestinationNum = 0

displayfc1 = Entry(root, state="readonly")
displayfc2 = Entry(root, state="readonly")
displayfc3 = Entry(root, state="readonly")
displayfc4 = Entry(root, state="readonly")
displayms1 = Entry(root, state="readonly")
displayms2 = Entry(root, state="readonly")

Any ideas on how anything could be changed or if the code is wrong? thanks!

Answer 1

This is not a minimal reproducible example. Something like this would have better explained your problem.

from tkinter import Tk, Entry

root = Tk()
my_entry = Entry(root, state='readonly')
my_entry.grid(row=0, column=0)
my_entry.insert(0, 500) # does not work

root.mainloop()

The problem is that your Entry widget is read only and cannot be updated. We can get around that by waiting until we have set a value and use the configure method to update the state after the fact.

from tkinter import Tk, Entry

root = Tk()
my_entry = Entry(root)
my_entry.grid(row=0, column=0)
my_entry.insert(0, 500)
my_entry.configure(state='readonly')

root.mainloop()

There are some other things that could be improved with your code like relegating your calculations to a helper function, having your entries in arrays, and setting your entries in a loop.

This is just an example as I don't have access to what's inside your variables.

# This makes it much easier to follow the logic
# of your calculation
def calculate(multiplier, crew, planet):
    return (multiplier - int(crew[1])) * planet[1]

multipliers = [100, 100, 100, 100, 150, 150]
# you could just append your entries to an array when creating them
# rather than add them here
entries = [displayfc1, 
           displayfc2, 
           displayfc3, 
           displayfc4, 
           displayms1, 
           displayms2
           ]

# zipping them up allows you to iterate through all
# of them at once
for entry, mult, crew, row in zip(entries, 
                                  multipliers, 
                                  crewInfo, 
                                  range(14, 20)
                                 ):
    entry.grid(row=row, column=2)
    entry.insert(0, calculate(mult, crew, planetInfo[getDestinationNum]))
    entry.configure(state='readonly')