How to convert elements in a list of list to lowercase?

Question

I am trying to convert the elements of a list of list of lowercase. This is what is looks like.

print(dataset)
[[\'It\', \'went\', \'Through\', \'my\', \'shi         


        

Answer 1

If you wish to convert all the Strings in your list in Python, you can simply use following code:

[w.lower() for w in My_List]

My_List is your list name

Answer 2

You have a nested structure. Either unwrap (if there is just one list contained, ever) or use a nested list comprehension:

[[w.lower() for w in line] for line in dataset]

The nested list comprehension handles each list in the dataset list separately.

If you have just one list contained in dataset, you may as well unwrap:

[w.lower() for w in dataset[0]]

This produces a list with the lowercased strings directly contained, without further nesting.

Demo:

>>> dataset = [['It', 'went', 'Through', 'my', 'shirt', 'And', 'came', 'out', 'The', 'back', 'and', 'hit', 'the', 'kid', 'behind', 'me', 'in', 'the', 'toe']]
>>> [[w.lower() for w in line] for line in dataset]
[['it', 'went', 'through', 'my', 'shirt', 'and', 'came', 'out', 'the', 'back', 'and', 'hit', 'the', 'kid', 'behind', 'me', 'in', 'the', 'toe']]
>>> [w.lower() for w in dataset[0]]
['it', 'went', 'through', 'my', 'shirt', 'and', 'came', 'out', 'the', 'back', 'and', 'hit', 'the', 'kid', 'behind', 'me', 'in', 'the', 'toe']

Answer 3

Either use map

map(str.lower,line)

Or list comprehension (which is basically syntactic sugar)

[x.lower() for x in line]

And this process can be nested for the entire dataset

[[x.lower() for x in line] for line in dataset]

And if you want to join all lines into one, use reduce:

reduce(list.__add__,[[x.lower() for x in line] for line in dataset])