Question

Using Python, I’m trying to convert a sentence of words into a flat list of all distinct letters in that sentence.

Here’s my current code:

words = 'She sells seashells by the seashore'

ltr = []

# Convert the string that is "words" to a list of its component words
word_list = [x.strip().lower() for x in words.split(' ')]

# Now convert the list of component words to a distinct list of
# all letters encountered.
for word in word_list:
    for c in word:
        if c not in ltr:
            ltr.append(c)

print ltr

This code returns ['s', 'h', 'e', 'l', 'a', 'b', 'y', 't', 'o', 'r'], which is correct, but is there a more Pythonic way to this answer, probably using list comprehensions/set?

When I try to combine list-comprehension nesting and filtering, I get lists of lists instead of a flat list.

The order of the distinct letters in the final list (ltr) is not important; what’s crucial is that they be unique.

Answer 1

Sets provide a simple, efficient solution.

words = 'She sells seashells by the seashore'

unique_letters = set(words.lower())
unique_letters.discard(' ') # If there was a space, remove it.