subverting imported libraries

test_a.py

# test_a.py
# in the bot, this represents the new hangups library
this_is_a_constant = 'ABCD'
def print_constant():
    print(repr(this_is_a_constant))
    

test_b.py

# test_b.py
# in the bot, this represents the plugin
import test_a

test_c.py

# test_c.py
# in the bot, this file is the plugin loader
import test_b # plugin is loaded
import test_d # we replace the test_a module inside the plugin with this in EXAMPLE 2

# EXAMPLE 1: replace constant
# setattr(test_b.test_a, 'this_is_a_constant', 'no longer constant');

# EXAMPLE 2: replace module
# setattr(test_b, 'test_a', test_d) # replaces module with another one

test_b.test_a.print_constant()
# in example 1, this prints 'no longer constant'
# in example 2, this prints '3.142'

test_d.py

# test_d.py
# in the bot, this replaces new hangups (test_a.py) with the compatibility layer
def print_constant():
    print('3.142');