sixtytrees - 10 months ago 47

Python Question

Python

`itertools.product()`

`l=[[1, a1**1,a1**2,..a1**b1],[1,a2**1,..a2**b2],..[1, an**1, an**2,..an**bn]]`

When I pass it to itertools.product() as an argument I don't get the desired result. How can I feed this list of lists of integers to product()?

`import itertools`

print([list(x) for x in itertools.product([1,2,4],[1,3])])

# [[1, 1], [1, 3], [2, 1], [2, 3], [4, 1], [4, 3]] #desired

l1=[1,2,4],[1,3] #doesn't work

print([list(x) for x in itertools.product(l1)])

#[[[1, 2, 4]], [[1, 3]]]

l2=[[1,2,4],[1,3]] #doesn't work

print([list(x) for x in itertools.product(l2)])

#[[[1, 2, 4]], [[1, 3]]]

Answer

You need to use `*l2`

within the `product()`

as `*`

unwraps the list. In this case, the value of `*[[1,2,4],[1,3]]`

will be `[1,2,4],[1,3]`

. Here's your code:

```
l2 = [[1,2,4],[1,3]]
print([list(x) for x in itertools.product(*l2)])
# Output: [[1, 1], [1, 3], [2, 1], [2, 3], [4, 1], [4, 3]]
```

Please check: What does asterisk mean in python. Also read regarding `*args`

and `**kwargs`

, you might find it useful. Check: *args and **kwargs in python explained

Source (Stackoverflow)