如何在 Tkinter 中将 output 更改为小写？

Question

I'm using Tkinter in python for the first time. I'm trying to make the output the user has entered lowercase. So if the enter "TEST" the output would be "test"

My code is:

from tkinter import *

# event functions (10:30 mins)
def onClickSubmitButton():                      # submit button event handler
        userEnteredText = textbox.get()         # get the enterd text from the Entry text box
        outputTextField.delete(0.0, END)        # (14:30 mins)delete all of the output field text contents
        outputTextField.insert(END, userEnteredText)  # (15:50 mins) output the user eneterd text




#main window (1:30 mins)
window = Tk()
window.title("Python Glossary")
window.configure(background="white")

# display text using - Label  (05:30 mins)
Label(window, text="Enter a string and press submit", bg="white", font="none 12 bold").grid(row=1,column=0,sticky=W) # using grid layout

# textbox for text entry - Entry (8:15 mins)
textbox = Entry(window, width=20, bg="white")
textbox.grid(row=2, column=0,sticky=W)          # grid position of textbox

# submit button - Button (9:30 mins) - calls onClickSubmitButton function when clicked
Button(window, text="SUBMIT", width=6, command=onClickSubmitButton ).grid (row=2,column=1, sticky =W)

#definitions - Label (11:50 mins)
Label(window, text="\n Your string", bg="white", font="none 12 bold").grid(row=4,column=0,sticky=W) # using grid layout

# output textField - Text(12:40 mins)
outputTextField = Text(window, width=75, height=6, wrap=WORD, background="white",)
outputTextField.grid(row=4, column=1,sticky=W)  # grid position of textField



# run the main loop
window.mainloop()

I tried:

outputTextField.insert.lower(END, userEnteredText)

but that didn't work. Any advice?

Answer 1

If you do outputTextField.insert(END, userEnteredText.lower()) then the entered text will be converted to lower case and then the insert function works as expected, taking the lowercase string as an argument.

Answer 2

in the most cases of these string methods you need to know, that you need to make a new variable for it.

def onClickSubmitButton():                      # submit button event handler
        userEnteredText = textbox.get()       # get the enterd text from the Entry text box
        low = userEnteredText.lower()
        outputTextField.delete(0.0, END)        # (14:30 mins)delete all of the output field text contents
        outputTextField.insert(END, low)  # (15:50 mins) output the user eneterd text

Answer 3

So here is a bit fancier option (I don't know if You need something like this but it also does what You ask for except no button has to be pressed to change characters to lowercase, in this case it will do that as the user is typing, try it out):

from tkinter import Tk, Text


def lower_input(event):
    if not event.char or r'\x' in repr(event.char):
        return
    text.delete('insert-1c')
    text.insert('insert', event.char.lower())


root = Tk()

text = Text(root)
text.pack()
text.bind('<Key>', lambda e: root.after(1, lower_input, e))

root.mainloop()

Basically it just binds the "<Key>" event to the text widget which means that when any key is pressed (and the focus is on the text widget) the event will be triggered which will then call the given function. Also .bind passes an event argument so that should be handled even if not used however here it is used to detect the character or to stop the function if the pressed key does not have a character (eg "Caps Lock" or "Backspace" (which actually has a bytes type thingy so that is why there is also the other comparison of r"\x" in repr(event.char) )). Then it just deletes the just written character and places a new one that is in lower case in its place. The root.after is used because the event is called before the character is typed to the Text widget meaning incorrect indexes are used so there is a tiny delay (1 ms) so that the character can appear on the screen and then the indexing happens.

EDIT: it is also possible to add or event.char.islower() (if that doesn't work could also try or not event.char.isupper() ) to that if statement to increase the performance a little bit since it won't go through the replacing process if the character is already lowercase

EDIT 2: as per PEP8 You should use snake_case for naming variables and functions and NOT camelCase

Useful sources/docs:

• this one specifically about indexes but contains a lot of other very useful stuff too
• simple docs I like to use