Pygame how to set up collision in my game, I dont understand it

Question

I know this question has been asked multiple times but I just cant wrap my head around the concept of collisions, now I know I am asking a lot but I will appreciate it greatly!, All I ask is someone to add collisions to my game and explain each step so I can try to understand whats going on,I tried youtube videos and they aren't explained very well or I just get overwhelmed which is what I feel right now, So I just want the player to stop when hitting the tree, something as simple as that! And if possible I want it to get the collision from a list for example I would have trees and other images in the list.

import pygame
import sys
import math
from pygame.locals import *
import tiles_list

pygame.init()
display_w = 800
display_h = 600

window = pygame.display.set_mode((display_w, display_h), HWSURFACE | DOUBLEBUF | RESIZABLE)
pygame.display.set_icon(pygame.image.load("game_icon.png"))
pygame.display.set_caption("Work in progress")
clock = pygame.time.Clock()
background = pygame.image.load("background.png")


class Player(object):
    """The controllable player in game"""

    def __init__(self, x, y, width, height, speed):
        self.x = x
        self.y = y
        self.width = width
        self.height = height
        self.image = pygame.image.load("sprite_sheet.png")
        self.speed = speed
        self.timer = 0
        self.frames = 1
        self.direction = 2

    def animation(self):
        x_coord = 50 * self.frames
        y_coord = 50 * self.direction
        self.character = self.image.subsurface(x_coord, y_coord, self.width, self.height)

        self.timer += 0
        if self.timer >= 10:
            self.timer = 0
            self.frames += 1
            if self.frames >= 9:
                self.frames = 1

    def draw(self):
        window.blit(self.character, (self.x, self.y))
        self.rect = pygame.Rect(self.x, self.y, self.width, self.height)

    def movement(self):
        self.keys = pygame.key.get_pressed()
        if self.keys[pygame.K_LEFT] or self.keys[pygame.K_a]:
            self.x -= self.speed
            self.direction = 1
            self.timer += 2
        if self.keys[pygame.K_RIGHT] or self.keys[pygame.K_d]:
            self.x += self.speed
            self.direction = 3
            self.timer += 2
        if self.keys[pygame.K_UP] or self.keys[pygame.K_w]:
            self.y -= self.speed
            self.direction = 0
            self.timer += 2
        if self.keys[pygame.K_DOWN] or self.keys[pygame.K_s]:
            self.y += self.speed
            self.direction = 2
            self.timer += 2
        if self.x >= 780:
            self.x = 780
            self.frames = 0
        if self.y >= 555:
            self.y = 555
            self.frames = 0
        if self.x <= 0:
            self.x = 0
            self.frames = 0
        if self.y <= 0:
            self.y = 0
            self.frames = 0


player = Player(400, 300, 50, 50, 4.5)


class Tree:
    def __init__(self, x, y, width, height):
        self.x = x
        self.y = y
        self.width = width
        self.height = height
        self.image = (
            pygame.transform.scale(tiles_list.tiles.subsurface(pygame.Rect(99, 147, self.width, self.height)),
                                   (62, 82)))

    def draw(self):
        window.blit(self.image, (self.x, self.y))


tree = Tree(348, 300, 42, 62)

running = True
while running:
    window.blit(background, (0, 0))
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
        if event.type == VIDEORESIZE:
            screen = pygame.display.set_mode((event.w, event.h), RESIZABLE)
        elif event.type == pygame.KEYUP:
            if player.keys:
                player.frames = 0

    dist_x = math.hypot(tree.x - player.x)
    dist_y = math.hypot(tree.y - player.y)  # Does nothing except calculate the distence
    print("distx", dist_x, "disty", dist_y)

    tree.draw()
    player.movement()
    player.animation()
    player.draw()

    clock.tick(60)
    pygame.display.flip()

Answer 1

I am willing to explain you the process of collisions. In your game you have two objects - the tree and the player. So, you can say that if the x and y coordinates of the player are the same , then there occurs a collisions. You can use this concept and create variables for detecting collisions. Thanks

Answer 2

Fist of all I suggest that you start to try to implement the collision test, before you ask a question. If you get stuck, you can ask a question about the code that gets you stuck.
Anyway I'll give you some hints.

In common the collision detection is based on pygame.Rect. For instance create a rectangle from pygaem.Surface objects player.image and tree.image by get_rect(). Evaluate if the 2 objects are colliding by colliderect():

player_rect = player.image.get_rect(topleft = (player.x, player.y))
tree_rect = tree.image.get_rect(topleft = (tree.x, tree.y))
if player_rect.colliderect(tree_rect):
    print("hit")

If you "just want the player to stop when hitting the tree", the store the position of the player and move the player. After that evaluate if the player hits the tree. If the player is hitting, then restore the position:

while running:
    # [...]

    # store position of player
    player_pos = (player.x, player.y)
    
    # move player
    player.movement()

    player_rect = player.image.get_rect(topleft = (player.x, player.y))
    tree_rect = tree.image.get_rect(topleft = (tree.x, tree.y))
    
    # test collision of player and tree
    if player_rect.colliderect(tree_rect):

        # restore player position
        (player.x, player.y) = player_pos 

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See also How to detect collisions between two rectangular objects or images in pygame