Python - Functions & Execution order

Question

I want to use the bot_create function with a button but I keep getting (on line 20) the problem "bots not defined" so I moved the function down below the button but got the problem "bot_create not defined". I didn't get this problem using C++ and I'm new to Python. How should I arrange the functions?

import tkinter as tk
import numpy as np
import multiprocessing as mp


bots_max = 1000 # Maximum number of bots
bot = []
bot_count = 0

# Menu functions
def save_field():
    pass

# Field functions
def field_clear():
    pass

# Bots functions
def bots_create():
    bot[bot_count] = bots
    bot_count += 1

main = tk.Tk()

field_sides = 600
ctrls_width = 200
main.geometry("800x600")
main.resizable(0, 0)
main.title("Swarm Simulator v1.0")



# Controls menu on left side
button1 = tk.Button(main, text = "Button 1").pack(side = "left", command = bots_create())



class environment:

    def __init__():
        pass

    class wall:
        def __init__():
            pass

# Bots
class bots:

    alive = True

    def __init__():
        alive = True



# Field where bots live
field = tk.Canvas(main, width = field_sides, height = field_sides, bg = "white").pack(side = "right")
for particle in bots:
    print("|")

main.mainloop()

Answer 1

Here's a version of your code that fixes all the syntactic problems, and so compiles (what I really mean is that my IDE now thinks its ok). It also runs, but I don't know if it does what you intended. See my comments in the code:

import tkinter as tk
import numpy as np
import multiprocessing as mp


# moved your class defs up to fix problems with accessing them before they are defined

class environment:

    def __init__(self):   # need a self param here
        pass

    class wall:
        def __init__(self):   # need a self param here
            pass

# Bots
class bots:

    alive = True

    def __init__(self):   # need a self param here
        alive = True

bots_max = 1000 # Maximum number of bots
bot = []
# bot_count = 0  # this no longer does anything.  use `len(bot)` to get the number of objects in the 'bot' list

# Menu functions
def save_field():
    pass

# Field functions
def field_clear():
    pass

# Bots functions
def bots_create():
#    bot[bot_count] = bots   # this will crash as it is referring to a non-existent location in the list
                             # also, your use of "bots" here makes no sense
#    bot_count += 1          # this makes 'bot_count' a local variable, which is not what you want
    bot.append(bots())       # not sure this is what you want, but this creates a new 'bots' object and adds it to the 'bot' list

main = tk.Tk()

field_sides = 600
ctrls_width = 200
main.geometry("800x600")
main.resizable(0, 0)
main.title("Swarm Simulator v1.0")



# Controls menu on left side
button1 = tk.Button(main, text = "Button 1").pack(side = "left", command = bots_create())



# Field where bots live
field = tk.Canvas(main, width = field_sides, height = field_sides, bg = "white").pack(side = "right")
for particle in bot:   # maybe you want to iterate over the 'bot' list instead of the 'bots' type?
    print("|")

main.mainloop()

As @khelwood says, it seems that you should swap the use of the names bot and bots per the way you are using them