Making Python Less Random
Andrew Healey discussed debugging a Python game prototype with randomness bugs. He used ptrace to control system calls, ensuring consistent results for random functions without altering the code, enabling deterministic debugging.
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In July 2024, Andrew Healey shared his experience of debugging a Python game prototype with tricky randomness bugs. He identified sources of randomness in his code and explored methods to achieve deterministic debugging without altering the code. By intercepting system calls using ptrace, he controlled the output of getrandom calls, ensuring consistent results for os.urandom and random.randint functions. Through a detailed explanation of the process, he demonstrated how to manipulate the Python process to return specific values, enabling deterministic outcomes for random number generation. This approach allowed for predictable results each time the Python process restarted, showcasing a method to handle randomness in Python programs without modifying the code directly. Andrew's exploration of system call tracing and manipulation provides insights into the inner workings of Python's randomness and offers a practical solution for deterministic debugging in Python applications.
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Making Python Less Random
Andrew Healey detailed his debugging journey with a Python game prototype facing randomness issues. He used ptrace to control system calls, ensuring consistent results without changing the code, showcasing advanced system call tracing techniques.
3 commentsTrivial (and terrible) example – on every run past the first, the lists are identical:
#!/usr/bin/env python3
import pickle
import random
SEED = 42
if __name__ == "__main__":
r = random.Random(SEED)
rand_l = None
new_rand_l = []
try:
with open("rand_list.dat", "rb") as f:
rand_l = pickle.load(f)
except FileNotFoundError:
pass
for i in range(100):
new_rand_l.append(r.randint(0, 1000))
if rand_l is not None:
assert rand_l == new_rand_l
else:
with open("rand_list.dat", "wb") as f:
pickle.dump(new_rand_l, f)
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Making Python Less Random
Andrew Healey detailed his debugging journey with a Python game prototype facing randomness issues. He used ptrace to control system calls, ensuring consistent results without changing the code, showcasing advanced system call tracing techniques.