Here is how you would do this with a nested list comprehension: 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].
How it works: array.insert(index, value) Insert an item at a given position. The first argument is the index of the element before which to insert, so array.insert(0, x) inserts at the front of the list, and array.insert(len(array), x) is equivalent to array.append(x).Negative values are treated as being relative to the end of the array.
Build a new list with a list comprehension: You can modify the original list in-place if you want, but it doesn’t actually save time: Here are (Python 3.6.3) timings demonstrating the non-timesave: And Python 2.7.6 timings:
Try this: In C#, arrays have a Length property, anything implementing IList<T> (including List<T>) will have a Count property.
Do this: In Python 3+, many processes that iterate over iterables return iterators themselves. In most cases, this ends up saving memory, and should make things go faster. If all you’re going to do is iterate over this list eventually, there’s no need to even convert it to a list, because you can still iterate … Read more
I’m trying to read a CSV file into a list of lists (of strings), pass it around for getting some data from a database, build a new list of lists of new data, then pass that list of lists so it can be written to a new CSV file. I’ve looked all over, and I can’t … Read more
Not the most efficient one, but by far the most obvious way to do it is: if order is significant you can do it with list comprehensions like this: (only works for equal-sized lists, which order-significance implies).
You can use the + operator to combine them: Output:
How about this?
Possible Duplicate:Get difference from two lists in Python What is a simplified way of doing this? I have been trying on my own, and I can’t figure it out. list a and list b, the new list should have items that are only in list a. So: I tried writing code, but every time it … Read more