how to multiply two different array of integers in python?

Question

i have taken input in two different lists by splitting a line having integers 1 2

for eg 1 2

3 4

so now i have split it and kept it in lists , and want to multiply them like 1*3 +2*4, but when i try to do it , its giving me that it can only multiply integers and not lists !! help here

can't multiply sequence by non-int of type 'list'.. that's the error i am getting – when i do

c=sum(i*j for i, j in zip(a,b))

...

t=raw_input()
d =[]
for j in range(0,int(t)):
    c=0
    n=raw_input()
    s = raw_input()
    s1=raw_input()
    a=[]
    b=[]
    a.append( [int(i) for i in s.split(' ')])
    b.append([int(i) for i in s.split(' ')])
    d.append(sum(i*j for i, j in zip(a,b)))

for i in d:
    print i

that's my code

Post your code, since the sum(...) fragment is correct it must be that your splitting code is wrong. — user97370
– user97370, Commented Jun 7, 2009 at 6:58

Paolo Bergantino · Accepted Answer · 2009-06-07 07:00:42Z

8

You need:

>>> a = [1,2]
>>> b = [3,4]
>>> sum(i*j for i, j in zip(a,b))
11

edited Jun 7, 2009 at 7:00

Paolo Bergantino

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answered Jun 7, 2009 at 6:22

sykloid

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1 Comment

Hick Over a year ago

can't multiply sequence by non-int of type 'list'.. thats the error i am getting

SingleNegationElimination · Accepted Answer · 2013-01-03 13:42:08Z

3

You can do it in a pythonic way using sum, map and a lambda expression.

>>> a = [1,2]
>>> b = [3,4]
>>> prod = lambda a, b: a*b
>>> sum(map(prod, a, b))
11

the lambda a, b: a*b bit also has a special name in python, operator.mul

>>> import operator
>>> sum(map(operator.mul, a, b))
11

edited Jan 3, 2013 at 13:42

answered Jun 7, 2009 at 7:18

SingleNegationElimination

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Comments

Nick Dandoulakis · Accepted Answer · 2009-06-07 07:38:44Z

1

Is this what you want?

t=raw_input()
d =[]
for j in range(0,int(t)):
    #c=0
    #n=raw_input()
    s = raw_input()
    s1 =raw_input()
    a = [int(i) for i in s.split(' ')]
    b = [int(i) for i in s1.split(' ')] # <--s1 not s
    d.append(sum(i*j for i, j in zip(a,b)))

for i in d:
    print i

answered Jun 7, 2009 at 7:38

Nick Dandoulakis

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Comments

David Z · Accepted Answer · 2009-06-07 07:32:01Z

0

It has nothing to do with multiplying integers, but you should probably be using the extend method:

    a.extend([int(i) for i in s.split(' ')])
    b.extend([int(i) for i in s.split(' ')])

append just tacks its argument on to the list as its last element. Since you are passing a list to append, you wind up with a list of lists. extend, however, takes the elements of the argument list and adds them to the end of the "source" list, which is what it seems like you mean to do.

(There are a bunch of other things you could do to fix up this code but that's probably a matter for a different question)

answered Jun 7, 2009 at 7:32

David Z

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