How to control self.play run at specific time point - manim

Question

Suppose there are two self.play statements, the first starts at 1s, I want to the seconds start at precisely 3s from the begining.
Currently I use self.wait to control the steps:
self.wait(1)
self.play...... # first animation
self.wait(2) # because 1 + 2 = 3
self.play...... # second animation
However, because the first animation will take sometime (e.g. 1.5s) to finish, actually the second animation will start at 1 + 1.5 + 2 = 4.5s.
How can I make the second self.play start run at precisely 3s from the begining?
Thanks in advance.

Answer 1

Do you mean, this?
class SuccessionExample(Scene):
def construct(self):
number_line=NumberLine(x_min=-2,x_max=2)
triangle=RegularPolygon(3,start_angle=-PI/2)\
.scale(0.2)\
.next_to(number_line.get_left(),UP,buff=SMALL_BUFF)
text_1=TextMobject("1")\
.next_to(number_line.get_tick(-1),DOWN)
text_2=TextMobject("2")\
.next_to(number_line.get_tick(0),DOWN)
text_3=TextMobject("3")\
.next_to(number_line.get_tick(1),DOWN)
text_4=TextMobject("4")\
.next_to(number_line.get_tick(2),DOWN)
self.add(number_line)
self.play(ShowCreation(triangle))
self.wait(0.3)
self.play(
#The move of the triangle starts
ApplyMethod(triangle.shift,RIGHT*4,rate_func=linear,run_time=4),
AnimationGroup(
Animation(Mobject(),run_time=1),#<- one second pause
Write(text_1),lag_ratio=1 #<- then start Write animation
),
AnimationGroup(
Animation(Mobject(),run_time=2),#<- two seconds pause
Write(text_2),lag_ratio=1 #<- then start Write animation
),
AnimationGroup(
Animation(Mobject(),run_time=3),#<- three seconds pause
Write(text_3),lag_ratio=1 #<- then start Write animation
),
AnimationGroup(
Animation(Mobject(),run_time=4),#<- four seconds pause
Write(text_4),lag_ratio=1 #<- then start Write animation
),
)
self.wait()