3.py

import time
Ts = []
Ns = []
for multiple in range(1, 11):
    N = 10 * multiple
    Ns.append(N)
    STR_LENGTH = 3000
    root = Node('a'*STR_LENGTH)
    current = root
    N_trials = 10
    T_samples = []
    for i in range(N_trials):
        for j in range(N):
            node = Node('a'*STR_LENGTH)
            current.left = node
            current = node

        start = time.time()
        serialize(root)
        end = time.time()
        T = end - start
        T_samples.append(T)
    T = sum(T_samples) / N_trials
    Ts.append(T)


from matplotlib import pyplot as plt
plt.plot(Ns, Ts)
print(Ts)

Ts[-1] / Ts[0] # this ration should be about 10 if this is O(N)