Lack of understanding "graphX, = ax.plot"

[easayed]

Dear every member

I want to under stand the following line

graphX, = ax.plot([], [], 'b', label = 'X')

this line is written in the following code which is a part of program

from matplotlib import pyplot as plt

fig = plt.figure(figsize=(12, 6))
ax = plt.axes(xlim=(0,leng-1), ylim=(0, 1000))

ax.grid(True)

graphX, = ax.plot([], [], 'b', label = 'X')
graphY, = ax.plot([], [], 'r', label = 'Y')

many thanks for all

[micseydel]

This example might help:

>>> t = (1,)
>>> t
(1,)
>>> u, = (1,)
>>> u
1