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I'm not sure if I'm using the correct wording in my question but the situation I have is that I'm calling a function and passing a value to one of its named keyword arguments only if I have a value for it. A simplified example of how I'm currently doing it:
var_1 = data.get("var_1", None)
if var_1:
some_function(some_arg=var_1)
else:
some_function()
The function some_function() does not accept setting some_arg to None so I can only call the function with the named argument if I have a valid value for it.
The reason why the above is less desirable for me is that the actual function calls I'm making have a bunch (5+) of named arguments that I set. This results in repeating mostly similar function calls that differ by only one parameter.
Is there a better way/more Pythonic way to do this? I wish I could call the function and set all possible named parameters that I might wish to pass but, at runtime, only pass in the values that I actually have something for.
In case it matters, the function calls are to the AWS Python SDK (Boto3) so I can't alter the behavior of the function.
541
Python passes arguments neither by reference nor by value, but by assignment.
I would expect this to do as follows: Initialize 'list' as an empty list; call main (this, at least, I know I've got right...) Within defineAList(), assign certain values into the list; then pass the new list back into main() Within main(), call useTheList(list)
Python Arbitrary Arguments allows a function to accept any number of positional arguments i.e. arguments that are non-keyword arguments, variable-length argument list.
Python has *args which allow us to pass the variable number of non keyword arguments to function. In the function, we should use an asterisk * before the parameter name to pass variable length arguments.
What you can do is:
var_1 = data.get("var_1", None)
fun_kwargs = {'some_arg': var_1} if var_1 else {}
some_function(**fun_kwargs)
If you have multiple parameters you could do:
fun_kwargs = {}
if var1: fun_kwargs['some_arg1'] = var_1
if var2: fun_kwargs['some_arg2'] = var_2
if var3: fun_kwargs['some_arg3'] = var_3
some_function(**fun_kwargs)
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