Ann Molly Paul

Writing effective functions

For readability

1. Use variable arguments where possible e.g. def foo(*args)
2. Use foo(*arg_list) when calling functionfoo which unpacks the list of arguments.
3. Specify keyword arguments when changing default values in a function call rather than positional defaults.
• def foo(a,b, c=10, d=True) So, when you call it foo(3,4, c=20,d=False).
4. Python 3 syntactically can force keyword only arguments by using * as one of the arguments, enforcing all the arguments that follow to be keyword only
• def foo(a,b,*, c=10, d=True) Python 3 syntax– force keyword-only args.

For performance:

• No memory running out issue
• Less lines of code
• More readable

	def load(cities): 
		out = [] 
		for city in cities:
			out.append(city)
		return out 

Replace the lines struck out with, yield city . In the first implementation, you would get all the cities by:

	result = load(cities) 
	print result

And the second, we wouldnt need to store all the cities in memory. Instead you would use it as needed by calling it as follows:

print next(result)