Dynamical passing parameters to a function in Python

Question

I want to write a code that will check a dictionary for a key and if exist to set it to a function as a parameter.

def myFunction(*args, **kwargs):
 # do stuffs
 if('name' in kwargs):
 thisTitle = kwargs.pop('name') 
 print(thisTitle)
 ...
 return thisTitle
t = {}
if 'name' in t.keys() 
 and 'param1' in t.keys() 
 and 'param2' in t.keys():
 res = myFunction(name = t['name'], 
 myparam1 = t['param1'],
 secondPar = t['param2'])
elif 'name' in t.keys() 
 and 'param1' in t.keys():
 res = myFunction(name=t['name'], 
 myparam1=t[param1])
elif 'name' in t.keys():
 res = myFunction(name=t['name'])

What if I had 10 parameters? There must be a better way.

• Andrew: It appears you're aware of the **kwargs syntax, so maybe read this book.pythontips.com/en/latest/args_and_kwargs.html and loop over the dictionary inside your function?

Answer 1

Try this:

def myFunction(*args, **kwargs):
 # do stuffs
 if('name' in kwargs):
 thisTitle = kwargs.pop('name')
 print(thisTitle)
 if('param1' in kwargs):
 print(kwargs['param1'])
 if('param2' in kwargs):
 print(kwargs['param2'])
 # ...
 return thisTitle
t = {'name': "same_name"}
myFunction(**t)
t = {'name': 'same_name',
 'param1': 'val1',
 'param2': 'val2'}
myFunction(**t)

Output:

$ python3 stack.py 
same_name
same_name
val1
val2

Answer 2

I would also suggest using the default argument on pop rather than checking for existence: thisTitle = kwargs.pop('name', default); so you don't do both a in and a pop.

if('name' in kwargs):
 thisTitle = kwargs.pop('name')

Becomes:

thisTitle = kwargs.pop('name', None)

It might be better to use get rather than pop unless removing the key from the dictionary is an required effect:

thisTitle = kwargs.get('name', None)

Your function then would return None rather than producing a NameError when the name keyword argument is not provided.

• ioaniatr: Thanks @Dan D, very useful tip !! I was setting a default value always just before if