# List comprehension on a nested list?

I have this nested list:

```    l = [['40', '20', '10', '30'], ['20', '20', '20', '20', '20', '30', '20'], ['30', '20', '30', '50', '10', '30', '20', '20', '20'], ['100', '100'], ['100', '100', '100', '100', '100'], ['100', '100', '100', '100']]
```

Now, what I want to do is convert each element in a list to float. My solution is this:

```    newList = []
for x in l:
for y in x:
newList.append(float(y))
```

But can this be done using nested list comprehension, right?

what I've done is:

```    [float(y) for y in x for x in l]
```

But then the result is bunch of 100's with the sum of 2400.

any solution, an explanation would be much appreciated. Thanks!

Here is how you would do this with a nested list comprehension:

```    [[float(y) for y in x] for x in l]
```

This would give you a list of lists, similar to what you started with except with floats instead of strings. If you want one flat list then you would use `[float(y) for x in l for y in x]`.

From: stackoverflow.com/q/18072759

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