plt.xlabel('length') code example

Example 1: set axis labels python

# Basic syntax:
plt.xlabel("X axis label") # Add ", fontsize = #" to control fontsize
plt.ylabel("Y axis label")

# Example usage:
plt.plot(range(5))
plt.xlabel("X axis label")
plt.ylabel("Y axis label")
plt.title("Figure title", fontsize = 20)

# Note, xlabel and ylabel come from matplotlib.pyplot and plt is an 
# 	abbreviation for this, e.g. import matplotlib.pyplot as plt

Example 2: matplotlib plot title font size

from matplotlib import pyplot as plt    

fig = plt.figure()
plt.plot(data)
fig.suptitle('test title', fontsize=20)
plt.xlabel('xlabel', fontsize=18)
plt.ylabel('ylabel', fontsize=16)
fig.savefig('test.jpg')