How can I check if an entry in tkinter has one or more zeros

user_17463921 0
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I'm just starting programming. I'm want to do a simple Ohm's law calculator. I'm struggling to check if the entry is empty or if it has one or more zeros in it. How can I check if it has one or more zeros in it?

from tkinter import *
import math as m

def doMath():
   U = entryU.get()
   I = entryA.get()
   if I == "0" or \
      I == "" or \
      U == "":                                                        
      labelR.config(text="Error", bg= "red")   
   else:                                              
      R = float(U)/float(I)                                       
      labelR.config(text="Resistance: {:.2f}\u03A9".format(R), bg="white")

frame = Tk()
entryU = Entry(frame)
entryU.place (x=95, y= 60, width= 250, height =30)

entryA= Entry(frame)
entryA.place(x=95, y=100, width= 250, height=30)

buttonMath = Button(frame, text="R",command = doMath)
buttonMath.place(x=360, y=70, width=120, height=50)

labelR = Label (frame, text="Resistance: ")
labelR.place(x=10, y= 145) 

frame.mainloop()

That's what I have but as soon as I have "00" in my string this won't work obviously and if I try to just check if I==0 it won't work because I can't compare string with a int (I suppose). I also want to be able to calculate with decimal numbers. Thanks for any help!

tkinter-entry tkinter python
3 Answers

If you want to check how many "0" you have in your string you can use return string.count("0") thanks @martineau for educating me :)

def check_zeros(string):
    return string.count("0")

print(check_zeros("0Lol00xD13202130110"))
user_141430740

In this scenario, rather than check for specific errors in one or the other Entry widgets, that it would be better to just handle the case where either one of them can't be converted into a float for any reason — because that's all the really matters.

If an error occurs trying to do the conversions, then you could try to diagnose the problem and maybe pop-up a messagebox or something with additional error information. However, if you think about it, there are huge number of ways to have entered something invalid, so I'm not sure it would be worth the trouble.

Note that you still might want to check for potential value problems after successful conversion, like I being 0.

Anyway, here's how to implement the simple approach I suggested initially:

from tkinter import *
import math as m

def doMath():
    U = entryU.get()
    I = entryA.get()
    try:
        R = float(U) / float(I)
    except ValueError:
        labelR.config(text="Error", bg= "red")
        return
    labelR.config(text="Resistance: {:.2f}\u03A9".format(R), bg="white")


frame = Tk()
frame.geometry('500x200')
entryU = Entry(frame)
entryU.place(x=95, y=60, width=250, height=30)

entryA = Entry(frame)
entryA.place(x=95, y=100, width= 250, height=30)

buttonMath = Button(frame, text="R", command=doMath)
buttonMath.place(x=360, y=70, width=120, height=50)

labelR = Label(frame, text="Resistance: ")
labelR.place(x=10, y= 145)

frame.mainloop()
user_3552300

Sorry, you should make that a list so you can count how many 0s are in there:

def doMath():
    U = entryU.get()
    I = entryA.get()
    splttedI = []
    for x in I:
       if x == 0:
            splyttedI.append(x)
    howmanytimes = len(splttedI)
    if "0" in splttedI or \
       I == "" or \
       U == "":                                                        
       labelR.config(text="Error", bg= "red")   
    else:                                              
        R = float(U)/float(I)                                              
        labelR.config(text="Resistance: {:.2f}\u03A9".format(R), bg="white")
user_132857070
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