CODEWITHSUNDEEP
python
DarsAE
DarsAE

Reputation: 185

Loop in two lists

I have these lists:

list1 = [3, 5, 2, 1, 9]
list2 = [6, 9, 1, 2, 4]
list3 = []
list4 = []

and I want to pass these formula:

x = a/b
y = 1/b

in which a is every value in list1 and b is every value in list2 and append the result of calculations into two empty lists - list3 and list4.

This is what I have but it's a disaster haha :(

u = 0
while u<len(list1):
    for a in list1:
        for b in list2:
            x = a/b
            y = 1/b
            u+=1
            list3.append(x,)
            list4.append(y,)

Anyone can help me with this?

Upvotes: 2

Views: 19248

Answers (5)

ICE BLUE
ICE BLUE

Reputation: 1

list3 = map((lambda x, y: x/y), list1, list2)
list4 = map(lambda x: 1/x), list2)

OR:

list3, list4 = zip(*map((lambda x, y: (x/y, 1/y)), list1, list2)

Upvotes: 0

ovgolovin
ovgolovin

Reputation: 13410

Here is a oneliner:

>>> list3,list4 = zip(*[(a/b,1/b) for a,b in zip(list1,list2)])
>>> list3
(0, 0, 2, 0, 2)
>>> list4
(0, 0, 1, 0, 0)

The output are tuples. But they can be easily converted to list.

Oh. It may be made even more memory efficient by using generator expression instead of list comprehension:

>>> zip(*((a/b,1/b) for a,b in zip(list1,list2)))

Upvotes: 9

Ned Batchelder
Ned Batchelder

Reputation: 375504

for a, b in zip(list1, list2):
    x = a/b
    y = 1/b
    list3.append(x)
    list4.append(y)

This is assuming you meant you wanted to use the lists pair-wise. If instead you meant you wanted every possible pairing of the lists, then:

for a in list1:
    for b in list2:
        x = a/b
        y = 1/b
        list3.append(x)
        list4.append(y)

Upvotes: 5

Charles Menguy
Charles Menguy

Reputation: 41428

Just use the zip function in Python:

for a, b in zip(list1, list2):
    list3.append(a/b)
    list4.append(1/b)

Upvotes: 4

frazman
frazman

Reputation: 33223

for a,b in zip(list1,list2):
  x = a/b
  y = 1/b

?? something like this

Upvotes: 4

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