How to make enemy follow player

Question

I found information about pygame, but i cant interpret this in tkinter.
icons - https://i.stack.imgur.com/ZcRvh.jpg
pastebin - https://pastebin.com/ykUzj9Pc

def key_pressed(event):
    global e
    if event.keysym == 'Up':
        move_wrap(player, (0, -step))
    if event.keysym == 'Down':
        move_wrap(player, (0, step))
    if event.keysym == 'Left':
        move_wrap(player, (-step, 0))
    if event.keysym == 'Right':
        move_wrap(player, (step, 0))
    check_move()
    # for enemy in enemies:
    #     direction = enemy[1]() # вызвать функцию перемещения у "врага"
    #     move_wrap(enemy[0], direction) # произвести  перемещение 
    #     print(e)
    for enemy in enemies:
        direction = enemy[1]()
        move_wrap(enemy[0], direction)
        list_ = [(step, 0), (-step, 0), (0, step), (0, -step)]
        predictions = []
        for i in list_:
            predictions.append([canvas.coords(enemy[0])[0] + i[0], canvas.coords(enemy[0])[1] + i[1]])
        for i in predictions:
            if i[0] - canvas.coords(player)[0] > i[1] - canvas.coords(player)[1]:
                if predictions.index(i) == 1:
                    move_wrap(enemy[0], (step, 0))
                elif predictions.index(i) == 2:
                    move_wrap(enemy[0], (-step, 0))
                elif predictions.index(i) == 3:
                    move_wrap(enemy[0], (0, step))
                elif predictions.index(i) == 4:
                    move_wrap(enemy[0], (0, -step))
        predictions.clear()

I have a list with enemies. In this list i have tuple with (enemy, random_move function).

That’s a bit of a broad question. Do you have a basic algorithm, pseudocode, anything? — AMC, Jan 18 '20 at 21:49
Sorry if my comment wasn't clear, I was specifically asking about the whole have an enemy follow the player thing. — AMC, Jan 18 '20 at 22:00
I was thinking about subtracting x player and enemy and y player and enemy but how can I link the selection, honestly, I don't understand how to do it almost at all — Ozballer31, Jan 18 '20 at 22:04

furas · Accepted Answer · 2020-01-20T23:41:45.433

To follow player you have to calculate vector between enemy and player, and normalize this vector (so its lenght will be 1), and then you can multiplciate it by enemy's speed to get what distance it has to move

player_x, player_y = 0, 0
enemy_x,  enemy_y  = 100, 100


diff_x = player_x - enemy_x
diff_y = player_y - enemy_y

distance = (diff_x**2 + diff_y**2)**0.5  # Pythagoras: a**2 + b**2 = c**2

normal_x = diff_x/distance
normal_y = diff_y/distance

print(normal_x, normal_y)

enemy_speed = 5

enemy_move_x = enemy_speed * normal_x
enemy_move_y = enemy_speed * normal_y

print(enemy_move_x, enemy_move_y)

You may have to also check if distance is not zero because you may get ZeroDivisionError: division by zero

EDIT: Minimal working example - use keys WASD to move green circle and red circle will follow.

import tkinter as tk
import random

def follow(player_x, player_y, enemy_x, enemy_y, enemy_speed=5):
    diff_x = player_x - enemy_x
    diff_y = player_y - enemy_y

    distance = (diff_x**2 + diff_y**2)**0.5  # Pythagoras: a**2 + b**2 = c**2

    if distance <= enemy_speed:
        return diff_x, diff_y

    normal_x = diff_x/distance
    normal_y = diff_y/distance

    enemy_move_x = enemy_speed * normal_x
    enemy_move_y = enemy_speed * normal_y

    return enemy_move_x, enemy_move_y

def on_key_press(event):
    global player_move_x
    global player_move_y

    if event.char == 'w':
        player_move_y -= 5
    if event.char == 's':
        player_move_y += 5
    if event.char == 'a':
        player_move_x -= 5
    if event.char == 'd':
        player_move_x += 5

def on_key_release(event):
    global player_move_x
    global player_move_y

    if event.char == 'w':
        player_move_y -= -5
    if event.char == 's':
        player_move_y += -5
    if event.char == 'a':
        player_move_x -= -5
    if event.char == 'd':
        player_move_x += -5

def update_game():
    global player_x
    global player_y
    global enemy_x
    global enemy_y

    player_x += player_move_x
    player_y += player_move_y
    canvas.move(player_id, player_move_x, player_move_y)

    enemy_move_x, enemy_move_y = follow(player_x, player_y, enemy_x, enemy_y, enemy_speed)
    enemy_x += enemy_move_x
    enemy_y += enemy_move_y
    canvas.move(enemy_id, enemy_move_x, enemy_move_y)

    root.after(100, update_game)

# --- main ---

player_x = 250
player_y = 250
player_move_x = 0
player_move_y = 0

enemy_x = random.randint(0, 500)
enemy_y = random.randint(0, 500)
enemy_speed = 5

root = tk.Tk()

canvas = tk.Canvas(root, width=500, height=500, bg='gray')
canvas.pack()
root.bind('<KeyPress>', on_key_press)
root.bind('<KeyRelease>', on_key_release)

player_id = canvas.create_oval(player_x-5, player_y-5, player_x+5, player_y+5, fill='green')
enemy_id = canvas.create_oval(enemy_x-5, enemy_y-5, enemy_x+5, enemy_y+5, fill='red')

update_game()

root.mainloop()

How to make enemy follow player

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