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I have a signal handler to handle ctrl-c interrupt. If in the signal handler I want to read a variable set in my main script, is there an alternative to using a "global" statement when setting the variable?
I don't mind doing this, but read this post (Do you use the "global" statement in Python?) in which someone commented that there should be no reason to ever use global.
What is the alternative in this case?
My code looks like this:
def signal_handler(signal, frame): print "in sig handler - g_var=%s" % g_var def main(): global g_var g_var = "test" time.sleep(120) if __name__ == '__main__': signal.signal(signal.SIGINT, signal_handler) main() 
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Parameter passing - allows the values of local variables within the main program to be passed to sub-programs without the need to use global variables. The value of these variables (or a copy of the value of these variables) is passed as a parameter to and from sub-programs as necessary.
Using global variables causes very tight coupling of code. Using global variables causes namespace pollution. This may lead to unnecessarily reassigning a global value. Testing in programs using global variables can be a huge pain as it is difficult to decouple them when testing.
You can access the global variables from anywhere in the program. However, you can only access the local variables from the function. Additionally, if you need to change a global variable from a function, you need to declare that the variable is global. You can do this using the "global" keyword.
The simplest way to avoid globals all together is to simply pass your variables using function arguments. As you can see, the $productData array from the controller (via HTTP request) goes through different layer: The controller receives the HTTP request. The parameters are passed to the model.
You can use a closure as the signal handler that acquires its state from the main script:
import signal import sys import time def main_function(): data_for_signal_handler = 10 def signal_handler(*args): print data_for_signal_handler sys.exit() signal.signal(signal.SIGINT, signal_handler) # Or whatever signal while True: data_for_signal_handler += 1 time.sleep(0.5) if __name__ == '__main__': main_function() You can use partial to create a "closure".
import signal from functools import partial def signal_handler(g_var, signal, frame): print "in sig handler - g_var=%s" % g_var def main(): g_var = "test" signal.signal(signal.SIGINT, partial(signal_handler, g_var)) time.sleep(120) if __name__ == '__main__': main() If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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