Python - dynamically calling a method with a dynamic number of arguments. Reflection?

Question

Say I want to parse a text file that has lines:

sampleMethod 
sampleParameter
sampleParameter2

where sampleMethod is a string of a method and sample parameters can be any type values.

I know I can use getattr to dynamically call something givn we know the module and method name:

output = getattr(componentName, sampleMethod)(sampleParameter)

but how can I do this if there are multiple parameters we discover dynamically?

So for example if the text file has:

sampleMethod 
sampleParameter
sampleParameter2
sampleParameter3

how can we do someting like this dynamically?

  output = getattr(componentName, sampleMethod)(sampleParameter, sampleParameter2, sampleParameter3)

Onilton Maciel · Accepted Answer · 2015-11-06 03:50:11Z

1

You could unpack your argument lists (the special *) :

# you could dynamically build the list 
parameterList = [sampleParameter, sampleParameter2, sampleParameter3]

# then pass as parameter
output = getattr(componentName, sampleMethod)(*parameterList)

Note that you do not have to use arbitrary argument lists if you are sure that parameterList will not be bigger than the number of parameters of sampleMethod (otherwise you can get an runtime error).

If you are not sure, you can still just slice the list first or use arbitrary argument lists.

edited Nov 6, 2015 at 3:50

answered Nov 6, 2015 at 3:37

Onilton Maciel

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Comments

Xiaoqi Chu · Accepted Answer · 2015-11-06 03:40:03Z

0

You could use * in the attribute of the function definition. It will treat all argument which are not matched into a tuple. For example:

def print_for(*args):
    print args

print_for(1,2,3)
print_for(1,2,3,4)

answered Nov 6, 2015 at 3:40

Xiaoqi Chu

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Ashish Kumar Gupta · Accepted Answer · 2023-07-17 16:45:54Z

0

from importlib.machinery import SourceFileLoader

inputParams = ["1st_param", "2nd_param", ....]
module=SourceFileLoader("module_name","absolute/path/to/pyfile").load_module()
method = getattr(module, "functionname")
result = method(*inputParams)
print(result)

edited Jul 17, 2023 at 16:45

answered Jul 17, 2023 at 16:43

Ashish Kumar Gupta

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