Python 3.3 GUI程序

Question

Celsius to Fahrenheit-- Write a GUI program that converts Celsius temperatures to Fahrenheit temperatures. The user should be able to enter a Celsius temperature, click a button, and then see the equivalent Fahrenheit temperature. Use the following formula to make the conversion: F = 9/5C +32 F is the Fahrenheit temperature and C is the Celsius temperature.

THIS IS THE CODE I HAVE SO FAR, THE ERROR I GET says "invalid literal for int() with base 10: ''" I need help getting it to run correctly.

#import
#main function
from tkinter import *
def main():
    root=Tk()

    root.title("Some GUI")
    root.geometry("400x700")
    #someothersting=""
    someotherstring=""
#enter Celcius
    L1=Label(root,text="Enter a Celcius temperature.")
    E1=Entry(root,textvariable=someotherstring)
    somebutton=Button(root, text="Total", command=convert(someotherstring))

    somebutton.pack()
    E1.pack()
    L1.pack()
    root.mainloop()#main loop


#convert Celcius to Fahrenheit
def convert(somestring):
    thestring=""
    thestring=somestring
    cel=0
    far=0
    cel=int(thestring)
    far=(9/5*(cel))+32
    print(far)

Answer 1

Your main problem is this line;

somebutton=Button(root, text="Total", command=convert(someotherstring))

...which will call convert(someotherstring) immediately and assign the result to command. Since someotherstring is empty when this line is reached, it will fail to convert the value and fail the program.

If you don't want it evaluated immediately but instead on button press, you can use a lambda as a command;

somebutton=Button(root, text="Total", command=lambda: convert(E1.get()))

...which will eliminate the use of someotherstring completely and just call convert with the contents of E1 when the button is clicked.

Answer 2

This could be due to int("")

In main(), do

def main():
    # ...
    someotherstring = 0 # Since its trying to get int

Or you can check if its empty in convert() :

def convert(somestring):
    if somestring != "":    
        # cel=0 dont need these in python
        # far=0
        cel=int(somestring)
        far=(9/5*(cel))+32
        print(far)

Note: Check if you are using someotherstring properly with Entry widget. I believe you are supposed to use StringVar() and do stringvar.get() to get the text inside widget.