Pandas - send warnings when data's shape changes

Question

I am using opendata, and sometimes the shape of the datasets changes : some rows are missing for example. I would like to be warned when it happens.

I figured this out :

import pandas as pd

old_data = [["apple",1,"red"], ["banana", 5, "yellow"], ["peach", 3, "pink"]]
new_data = [["apple",1,"red"], ["banana", 5, "yellow"], ["peach", 3, "pink"],
               ["orange", 7, "orange"]]

old_dataset = pd.DataFrame(old_data, columns = ["fruit", "nb", "colour"])
new_dataset = pd.DataFrame(new_data, columns = ["fruit", "nb", "colour"])

compare_lengths = len(old_dataset) == len(new_dataset)

if compare_lengths == False:
    lengths_warning = "Dataset's length changed"
if compare_lengths == True:
    lengths_warning = "OK"

Then I would gather all the warnings in a file, where I could see them all. I would do this by importing every variable like this.

from file_1 import lengths_warning

Is there a better way to do it ?

Is it possible to set up warnings/controls in a more efficient way ? With a specific module maybe ?

Thks