how to call methods with multiple arguments

Question

i am trying to learn python. in a method like average below how can call this method without supplying value for a means we only supply values for b. How will we call such a method.

def average(a=5 , *b):
    sum=0
    count=0
    print(" b is {0}".format(b))
    for bb in b:
        sum += bb
        count+=1
    av=(sum+a)/(count+1)
    return av

print("average is {0}".format(average(3,5,7,8,9,2)))

Here it takes a=3 and the rest as b. How can we call this method without value for a at all.

Can we have the first value as nargs like . If yes how do we supply the value of b.

def average(*a,b)

so you want to call it without a and with b? why? but i think average(b=(1,2,3)) should work... — M. Volf
– M. Volf, Commented Dec 4, 2017 at 16:58
" in a method like this how can call this method without supplying value for a" - Do you want a default value for a? — Chris
– Chris, Commented Dec 4, 2017 at 16:59

wim · Accepted Answer · 2017-12-04 16:58:23Z

3

def average(*a, b):
    ...

Using the syntax above, you must include b by keyword-only:

average(1,2,3,b=4)

If you don't like that, then just unpack inside the function directly like shown below:

def average(*args):
    *a, b = args
    ...

You will need to add handling for the case where args is empty.

answered Dec 4, 2017 at 16:58

wim

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8 Comments

Makoto Over a year ago

@MosesKoledoye: Given that Python 2.7 is nearing EOL in about 2 years... seems like a good time to migrate over.

user2779311 Over a year ago

what i have got from answers from all is if function is average(*a,b) then we need to specify average(1,2,3,b=4) and if we have average(a=5,*b) and we need to call without passing a then average(b=(2,3,4)). thanks

user2779311 Over a year ago

i am able to run average(1,2,3,b=4) but running average(b=(1,2,3)) is not working and generates an error TypeError: average() got an unexpected keyword argument 'b'. Can anybody update

wim Over a year ago

The first method shown in this answer already works with average(b=(1,2,3)). The argument a will take the empty tuple here.

user2779311 Over a year ago

@wim but second one is not working i.e average(a=5,*b) is not working for average(b=(1,2,3))

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