pygame draw function

Question

Apologies in advance if this is a simple fix but I couldn't find anything on it. I am relatively new to pygame but I can't understand why when I run this the first bar that is drawn is always half cut off. To me anyway I should start a 0,400 and draw from 0 across 40 and then up. If this is not the case please enlighten a curious mind

from pygame import *
import pygame, sys, random

pygame.init()
screen = pygame.display.set_mode((1000,400))
colour = (0, 255, 0)
array = []
x, y, z, b = -80, 0, 0, 0
flag = True
for c in range(5):
    array.append(random.randint(100, 400));

for c in array:
    print c

while True:

    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()

    if len(array) == z:
        flag = False

    if flag == True:
        b = array[z]
        x += 80
        z += 1

    pygame.draw.line(screen, colour, (x, 400), (x, (400-b)), 40)

    pygame.display.update()

If the goal is filling rect's, there is Surface.fill(Rect)

ninMonkey
– ninMonkey

2013-09-21 17:23:05 +00:00
Commented Sep 21, 2013 at 17:23 — ninMonkey
– ninMonkey, Commented Sep 21, 2013 at 17:23

unutbu · Accepted Answer · 2013-09-21 16:26:10Z

1

pygame is drawing a line from (0,400) to (0, 400-b), with line thickness 40.

Here is an way to shift the lines so each is fully visible:

for i, b in enumerate(array):
    x = i*80 + 20  # <-- add 20 to shift by half the linewidth
    pygame.draw.line(screen, colour, (x, 400), (x, (400-b)), 40)

import sys
import random
import pygame

pygame.init()
screen = pygame.display.set_mode((1000,400))
colour = (0, 255, 0)
array = [random.randint(100, 400) for c in range(5)]

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    linewidth = 40
    for i, b in enumerate(array):
        x = i*linewidth*2 + linewidth//2
        pygame.draw.line(screen, colour, (x, 400), (x, (400-b)), linewidth)

    pygame.display.update()

edited Sep 21, 2013 at 16:26

answered Sep 21, 2013 at 14:55

unutbu

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2 Comments

Silk Over a year ago

thanks for the repley @unutbu the for loop is a much cleaner way of creating the bars but i am stil perplexed as to why 'pygame.draw.line(screen, colour, (start, 400), (start, 200))' (start = 0) :) then add say 400 to start this still draws "half" the line compared to the second line drawn

unutbu Over a year ago

The coordinate (start, 400) represents a point in the middle of the line, not the lower left corner of the rectangular block drawn by the line. Pygame is drawing this line with a linewidth of 40, meaning that the line is thickened by 20 pixels to the left and 20 pixels to the right of (start, 400).

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