CODEWITHSUNDEEP
pythonpygame
Innkeeper
Innkeeper

Reputation: 673

TypeError: Wrong number of arguments

I'm introducing myself to python and the pygame library. I wanted to try a very basic particle emitter first, but I'm getting an error.

import pygame
import random

pygame.init()

screen = pygame.display.set_mode((640, 480))
clock = pygame.time.Clock()
running = True

color = (128, 128, 128)
radius = 10

class Particle:
    """Represents a particle."""

    def __init__(self, pos, vel):
        self.pos = pos
        self.vel = vel

    def move(self):
        self.pos += self.vel

    def draw(self):
        pygame.draw.circle(screen, color, self.pos, radius)

particles = list()

while running:
    for e in pygame.event.get():
        if e.type == pygame.QUIT:
            running = False

    screen.fill((0, 0, 0))

    if len(particles) < 10:
        randvel = random.randint(-5, 5), random.randint(-5, 5)
        p = Particle((0, 0), randvel)
        particles.append(p)

    for p in particles:
        p.move()
        p.draw()

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

To my understanding, this error says 2 arguments must be passed, not 4.

Traceback (most recent call last):
  File "D:\data\eclipse\pythonscrap\main.py", line 44, in <module>
    p.draw()
  File "D:\data\eclipse\pythonscrap\main.py", line 24, in draw
    pygame.draw.circle(screen, color, self.pos, radius)
TypeError: must be sequence of length 2, not 4

I suspect this is a common error with beginners, because it's easy to forget an extra set of () to make a tuple. But as I look at the documentation, I find that the method's signature is:

circle Found at: pygame.draw
pygame.draw.circle(Surface, color, pos, radius, width=0): return Rect
    draw a circle around a point

That's five arguments, with one given a default value. So what is going wrong here?

Upvotes: 0

Views: 2163

Answers (1)

Martijn Pieters
Martijn Pieters

Reputation: 1121884

Your argument count is correct. It is the pos tuple that is wrong, it has length 4 instead of 2.

By adding self.vel you add new elements to the tuple, not sum the coordinates:

self.pos += self.vel

Sum the individual coordinates instead:

self.pos = (self.pos[0] + self.vel[0], self.pos[1] + self.vel[1])

A quick demo to illustrate the problem:

>>> pos = (0, 0)
>>> vel = (1, 1)
>>> pos += vel
>>> pos
(0, 0, 1, 1)

Upvotes: 4

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