I think that you can just use the plt.text for those purposes. The code below uses it to obtain the result you want.
import matplotlib.pyplot as plt
import numpy as np
from matplotlib import rcParams
rcParams['font.family'] = 'serif'
rcParams['font.size'] = 16
A = [[1, 3, 4, 5, 6, 7],
[3, 3, 0, 7, 9, 2],
[1, 3, 4, 5, 6, 6]]
X = ["A", "B", "C", "E", "F", "G"]
Y = ["R", "S", "T"]
m = len(Y)
n = len(X)
plt.figure(figsize=(n + 1, m + 1))
for krow, row in enumerate(A):
plt.text(5, 10*krow + 15, Y[krow],
horizontalalignment='center',
verticalalignment='center')
for kcol, num in enumerate(row):
if krow == 0:
plt.text(10*kcol + 15, 5, X[kcol],
horizontalalignment='center',
verticalalignment='center')
plt.text(10*kcol + 15, 10*krow + 15, num,
horizontalalignment='center',
verticalalignment='center')
plt.axis([0, 10*(n + 1), 10*(m + 1), 0])
plt.xticks(np.linspace(0, 10*(n + 1), n + 2), [])
plt.yticks(np.linspace(0, 10*(m + 1), m + 2), [])
plt.grid(linestyle="solid")
plt.savefig("Table.png", dpi=300)
plt.show()
And, you get
