Use multiple lists as input arguments of a function (Python)

Question

I know that the property map(function,list) applies a function to each element of a single list. But how would it be if my function requires more than one list as input arguments?.

For example I tried:

   def testing(a,b,c):
      result1=a+b
      result2=a+c
      return (result1,result2)

a=[1,2,3,4]
b=[1,1,1,1]
c=[2,2,2,2]

result1,result2=testing(a,b,c)

But this only concatenates the arrays:

result1=[1,2,3,4,1,1,1,1]
result2=[1, 2, 3, 4, 2, 2, 2, 2]

and what I need is the following result:

result1=[2,3,4,5] 
result2=[3,4,5,6]

I would be grateful if somebody could let me know how would this be possible or point me to a link where my question could be answered in a similar case.

If you want to do mathematical operations on vectors, use a library such as numpy, especially if you are going to do this often. — Holt
– Holt, Commented Dec 2, 2015 at 15:04

CubeRZ · Accepted Answer · 2015-12-02 14:59:29Z

4

You can use operator.add

from operator import add

def testing(a,b,c):
    result1 = map(add, a, b)
    result2 = map(add, b, c)
    return (result1, result2)

answered Dec 2, 2015 at 14:59

CubeRZ

5745 silver badges9 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Holt Over a year ago

Be careful, on python 3.x map returns a generator not a list.

MaTh · Accepted Answer · 2015-12-02 15:00:50Z

4

You can use zip:

def testing(a,b,c):
    result1=[x + y for x, y in zip(a, b)]
    result2=[x + y for x, y in zip(a, c)]
    return (result1,result2)

a=[1,2,3,4]
b=[1,1,1,1]
c=[2,2,2,2]

result1,result2=testing(a,b,c)
print result1 #[2, 3, 4, 5]
print result2 #[3, 4, 5, 6]

answered Dec 2, 2015 at 15:00

MaTh

2171 silver badge13 bronze badges

Comments

Paul Siegel · Accepted Answer · 2015-12-02 15:11:32Z

2

Quick and simple:

result1 = [a[i] + b[i] for i in range(0,len(a))]
result2 = [a[i] + c[i] for i in range(0,len(a))]

(Or for safety you can use range(0, min(len(a), len(b)))

answered Dec 2, 2015 at 15:11

Paul Siegel

1,4112 gold badges16 silver badges37 bronze badges

Comments

Huy Nguyen · Accepted Answer · 2017-08-23 19:06:07Z

0

Instead of list, use array from numpy instead. list concatenate while arrays add corresponding elements. Here I converted the input to numpy arrays. You can feed the function numpy arrays and avoid the conversion steps.

def testing(a,b,c):
    a = np.array(a)
    b = np.array(b)
    c = np.array(c)
    result1=a+b
    result2=a+c
    return (result1,result2)

a=[1,2,3,4]
b=[1,1,1,1]
c=[2,2,2,2]

result1,result2=testing(a,b,c)

print(result1, result2)

answered Aug 23, 2017 at 19:06

Huy Nguyen

735 bronze badges

Collectives™ on Stack Overflow

Use multiple lists as input arguments of a function (Python)

4 Answers 4

1 Comment

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related