How to Change Legend Font Size in Matplotlib?

import matplotlib.pyplot as plt
import numpy as np

plt.figure(figsize = (8, 4))

x = ['Arjun', 'Bharath', 'Raju', 'Seeta', 'Ram']
y = [5, 7, 8, 4, 6]

plt.bar(x, y, color = 'g')

plt.xlabel('Students', fontsize = 18)
plt.ylabel('Marks', fontsize = 18)

#Default fontsize of text using legend
plt.legend(['Marks scored'])

plt.show()

import matplotlib.pyplot as plt
import numpy as np

plt.figure(figsize = (8, 4))

x = ['Arjun', 'Bharath', 'Raju', 'Seeta', 'Ram']

y = [5, 7, 8, 4, 6]

plt.bar(x, y, color = 'g')

plt.xlabel('Students', fontsize = 18)
plt.ylabel('Marks', fontsize = 18)

#Changing text fontsize in legend 
plt.legend(['Marks scored'], fontsize = 17)

plt.show()

import matplotlib.pyplot as plt

plt.figure(figsize = (8 , 5))

plt.plot([1, 2, 4, 8, 30, 1])
plt.plot([1, 6, 13, 20, 38, 1])
plt.plot([1, 4, 8, 14, 20, 1])
plt.plot([1, 3, 4, 5, 10, 1])

#Using prop keyword in legend to change font size
plt.legend(['blue', 'orange', 'green', 'red'], 
           prop = {'size' : 20}, 
           loc = 'upper left', shadow = True,
           facecolor = 'yellow')

plt.show()

import matplotlib.pyplot as plt
import numpy as np
from pylab import *

x = np.linspace(0, (2*np.pi), endpoint = True)

xlim(x.min(), x.max())

xticks([0, np.pi/2, np.pi, (3*np.pi/2), (2*np.pi)], 
       [r'$0$', r'$+\pi/2$', r'$+\pi$', r'$3/2\pi$', r'$2\pi$'])

ylim(-1, 0, 1)
yticks([-1, 0, +1], 
       [r'$-1$', r'$0$', r'$+1$'])

plt.plot(x, np.sin(x), label = "sin(x)")
plt.plot(x, np.cos(x), label = "cos(x)")

plt.title('Trigonometric Functions', fontsize = 22)

plt.xlabel('Angles', fontsize = 18)
plt.ylabel('Values', fontsize = 18)

plt.legend(loc = 'upper center')

plt.rc('legend', fontsize = 16)

#plt.grid()
plt.tight_layout()

plt.show()