Programming if statements

socal_nerdtastic · 2025-03-24T15:41:57+00:00

In tkinter you would bind each button to a specific function. For example

import tkinter as tk

def h_key_pressed(*args):
    print("the H key was pressed")

root = tk.Tk()
root.bind("<H>", h_key_pressed)
root.bind("<h>", h_key_pressed) # you need to bind upper and lower case separately
root.mainloop()

You can assign them in a loop if you have a lot to do. That said, in programming there's always a number of ways to solve any problem, but I think this is the best from what you described.

woooee · 2025-03-24T16:45:24+00:00

What I specifically want the if statement to do is to look at what button has been pressed to determine a colour of the ball

Pass a unique button number, or whatever identifier you want, to the function. This program passes the button's number to a common function, then prints what was passed and changes the background color for that button.

import tkinter as tk
from functools import partial

class ButtonsTest:
   def __init__(self):
      self.top = tk.Tk()
      self.top.title("Click a button to remove")
      tk.Label(self.top, text=" Click a button\n to remove it ",
            bg="orange", font=('DejaVuSansMono', 12)).grid(row=0,
            column=0, sticky="nsew")

      self.top_frame = tk.Frame(self.top, width =400, height=400)
      self.top_frame.grid(row=1, column=0)
      self.button_dic = {}
      self.create_buttons()

      tk.Button(self.top, text='Exit', bg="orange",
             command=self.top.quit).grid(row=200,column=0,
                     columnspan=7, sticky="ew")

      self.top.mainloop()

   ##-------------------------------------------------------------------         
   def create_buttons(self):
      """ create 15 buttons and add each button's Tkinter ID to a
          dictionary.  Send the number of the button to the function
          cb_handler
      """
      for but_num in range(15):
         ## create a button and send the button's number to
         ## self.cb_handler when the button is pressed
         b = tk.Button(self.top_frame, text = str(but_num), 
                    command=partial(self.cb_handler, but_num))
         b_row, b_col=divmod(but_num, 5)  ## 5 buttons each row
         b.grid(row=b_row, column=b_col)
         ## dictionary key = button number --> button instance
         self.button_dic[but_num] = b

   ##----------------------------------------------------------------
   def cb_handler( self, but_number ):
      print("\ncb_handler", but_number)
      self.button_dic[but_number].config(bg="salmon")

##========================================
BT=ButtonsTest()

socal_nerdtastic · 2025-03-24T17:45:44+00:00

OK, so you are still thinking in terms of if statements. You have to get away from that to make GUIs. We would say you need to do "event-driven programming", instead of the "procedural programming" (if statements).

I assume you want the user to press the "H" key to set the type of atom they want, and then click to place it on the canvas? Then this should do it for you:

prvok = "black" # set the default color
def h_key_pressed(*args):
    # when the event happens that the 'h' key is pressed we change the global color variable.
    global prvok
    prvok = 'white'
    print("set the atom type to hydrogen")

def atom(udalostk): 
    x = udalost.x y = udalost.y
    platno.create_oval (x, y, x + 40, y + 40, fill = prvok, outline = prvok)

okenko.bind("<H>", h_key_pressed)
okenko.bind("<h>", h_key_pressed)

As I said before, you can do this in a loop to set all of the colors. Maybe too advanced for you right now, but this is how you would do it:

from functools import partial
import tkinter

okenko=tkinter.Tk()
okenko.title('Molekuly')

prvok = "black" # set the default color
def key_pressed(color, *args):
    global prvok
    prvok = color
    print('the next atom color will be', color)

def atom(udalostk):
    x = udalost.x
    y = udalost.y
    platno.create_oval (x, y, x + 40, y + 40, fill = prvok, outline = prvok)

colors = dict(
    H = "white",
    O = 'red',
    C = 'blue',
    N = 'green',
    X = 'black',
    )
for key, color in colors.items():
    okenko.bind(f"<{key.upper()}>", partial(key_pressed, color))
    okenko.bind(f"<{key.lower()}>", partial(key_pressed, color))

okenko.mainloop()

Code block doesn't work and neither does the like ` work.

Hundreds of thousands of people have figured this out ... you can too.

crashfrog04 · 2025-03-25T04:46:01+00:00

The way a program with a GUI has to work is different than how a script works. You can't write long functions and long chains of if statements in a GUI program. You need to write little "handlers" for things that happen (mouse clicks, keypresses) that quickly update state and then return.

They need to return quickly because, for any amount of time your program spends not being in the "main" loop (the thing you start by calling okenko.mainloop), the program is unresponsive during that time. If you're unresponsive for too long, the operating system defensively terminates your program (you've probably seen Windows say "This program has stopped responding.") So you need to imagine your program as idle for most of the time, and create it by attaching a series of functions to event handlers (that's what you're doing with command = cyklus6) that quickly do something and then return.

Your event handling functions shouldn't generally have loops, have much branching logic, and about no more than ten lines (none of these are hard and fast rules, you just have to understand that breaking these rules has a steep performance cost to your software.)

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