pip install ismain

from ismain import is_main

#
# Same as:
# 
#     if "__name__" == __main__:
# 
# ... but more readable.
#
if is_main():
    print("Hello from main.")

The ismain function introduces some overhead compared to the native Python if __name__ == "__main__": construct. However, the absolute overhead is on the order of 10s of milliseconds on modern hardware, so it's generally negligible for many applications.

See the benchmark results for more details.