# doubling the width of markers
x = [0,2,4,6,8,10]
y = [0]*len(x)
s = [20*4**n for n in range(len(x))]
plt.scatter(x,y,s=s)
plt.show()

# doubling the area of markers
x = [0,2,4,6,8,10]
y = [0]*len(x)
s = [20*2**n for n in range(len(x))]
plt.scatter(x,y,s=s)
plt.show()

plt.scatter(2, 1, s=4000, c='r')
plt.scatter(2, 1, s=1000 ,c='b')
plt.scatter(2, 1, s=10, c='g')

import numpy as np
import matplotlib.pyplot as plt

x1 = np.random.randn(20)
x2 = np.random.randn(20)
plt.figure(1)
# you can specify the marker size two ways directly:
plt.plot(x1, 'bo', markersize=20)  # blue circle with size 10
plt.plot(x2, 'ro', ms=10,)  # ms is just an alias for markersize
plt.show()

import matplotlib.pyplot as plt
input_list = [{'x':100,'y':200,'radius':50, 'color':(0.1,0.2,0.3)}]
output_list = []
for point in input_list:
    output_list.append(plt.Circle((point['x'], point['y']), point['radius'], color=point['color'], fill=False))
ax = plt.gca(aspect='equal')
ax.cla()
ax.set_xlim((0, 1000))
ax.set_ylim((0, 1000))
for circle in output_list:
   ax.add_artist(circle)

import matplotlib.pyplot as plt

fig,ax = plt.subplots()

ax.plot([0],[0], marker="o",  markersize=10)
ax.plot([0.07,0.93],[0,0],    linewidth=10)
ax.scatter([1],[0],           s=100)

ax.plot([0],[1], marker="o",  markersize=22)
ax.plot([0.14,0.86],[1,1],    linewidth=22)
ax.scatter([1],[1],           s=22**2)

plt.show()

1 point == fig.dpi/72. pixels

import matplotlib.pyplot as plt

for dpi in [72,100,144]:

    fig,ax = plt.subplots(figsize=(1.5,2), dpi=dpi)
    ax.set_title("fig.dpi={}".format(dpi))

    ax.set_ylim(-3,3)
    ax.set_xlim(-2,2)

    ax.scatter([0],[1], s=10**2,
               marker="s", linewidth=0, label="100 points^2")
    ax.scatter([1],[1], s=(10*72./fig.dpi)**2,
               marker="s", linewidth=0, label="100 pixels^2")

    ax.legend(loc=8,framealpha=1, fontsize=8)

    fig.savefig("fig{}.png".format(dpi), bbox_inches="tight")

plt.show()