Make particles spawn continuously with Pygame

Crate a list for the particles:

particles = []

Use pygame.time.get_ticks() to get number of milliseconds since pygame.init() was called. Define the time at which the 1st particle must appear. If the time exceeds create a particle and set the time for the next particle to be created:

next_particle_time = 0

running = True
while running:
    # [...]

    current_time = pygame.time.get_ticks()
    if current_time > next_particle_time:
        particles.append(Particule((255,0,0), 100))         
        next_particle_time = current_time + 200    # 0.2 second interval

Draw and move all the particle in a loop:

running = True
while running:
    # [...]

    for p in particles[:]:
        p.update()
        p.random_movement()
        p.life()
        if p.radius < 1:
            particles.remove(p)

Complete example

import pygame, random

# -- Variables --
pygame.init()
clock = pygame.time.Clock()
fps_limit = 60.0
resx = 1600 
resy = 900
screen = pygame.display.set_mode([resx,resy])
pygame.display.set_caption("Baguette")

# -- Classes --
class Particule():
    def __init__ (self,color,radius):
        pygame.sprite.Sprite.__init__(self)
        self.color = color
        self.radius = radius
        self.position_x = random.randint(radius, 1600-radius)
        self.position_y = random.randint(radius, 900-radius)

    def update(self):
        pygame.draw.circle(screen, self.color, (self.position_x,self.position_y),self.radius)

    def random_movement(self):
        self.position_x += random.randint(-10,10)
        self.position_y -= random.randint(-5,5)

    def life(self):
        self.radius -= 1

# -- Objects --
particles = []
next_particle_time = 0

# -- Game loop --
running = True
while running:
    clock.tick(fps_limit)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    current_time = pygame.time.get_ticks()
    if current_time > next_particle_time:
        particles.append(Particule((255,0,0), 100))         
        next_particle_time = current_time + 200 # 0.2 second interval

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

    for p in particles[:]:
        p.update()
        p.random_movement()
        p.life()
        if p.radius < 1:
            particles.remove(p)
    print(len(particles))

    pygame.display.flip()   

pygame.quit()