How to iterate through a list of lists in python?

Question

I have a list of lists like this.

documents = [['Human machine interface for lab abc computer applications','4'],
             ['A survey of user opinion of computer system response time','3'],
             ['The EPS user interface management system','2']]

Now i need to iterate through the above list and output a list of strings, as shown below (without the numbers in the original list)

documents = ['Human machine interface for lab abc computer applications',
             'A survey of user opinion of computer system response time',
             'The EPS user interface management system']

Answer 1

The simplest solution for doing exactly what you specified is:

documents = [sub_list[0] for sub_list in documents]

This is basically equivalent to the iterative version:

temp = []
for sub_list in documents:
    temp.append(sub_list[0])
documents = temp

This is however not really a general way of iterating through a multidimensional list with an arbitrary number of dimensions, since nested list comprehensions / nested for loops can get ugly; however you should be safe doing it for 2 or 3-d lists.

If you do decide to you need to flatten more than 3 dimensions, I'd recommend implementing a recursive traversal function which flattens all non-flat layers.