Converting List to Set in Python! What am I doing wrong?

user_14055915 0
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I created a list with random letters(uppercase & lowercase). Im trying to write code so it only print the unique values considering the uppercase & lowercase. for example, ["A","a","a","B","b"] would print ["a","b"]

heres my code so far:

List_1 = ["a","a","a","b","A","b", "B", "c", "C"]
for x in List_1:
    l = x.lower()
    myset = set(l)
    print(myset)

& here is the output:

{'a'}
{'a'}
{'a'}
{'b'}
{'a'}
{'b'}
{'b'}
{'c'}
{'c'}

Now that im printing these value through a set, why is it still printing duplicate values? what am I doing wrong?

set python-3.x list python
3 Answers

You are doing wrong that you create a new set in each loop iteration.

Instead of

myset = set(l)

you want to use

myset.add(l)

and initialize myset = set() before the loop.

Alternatively, you can replace the whole loop by a set comprehension:

myset = {x.lower() for x in List_1}
user_46215130

You're taking every single element in the list, then making a set with that - each set has no knowledge of the other set.

Try something like this:

myset = set(l.lower() for l in List_1)

You'll end up with a true set.

user_78716850

Your current solution iterates over the list and creates a singleton set for each item in the list, which it then prints and throws away.

To convert a list to a set, simply write set(the_list).

In your case, you first want to transform the list (by lower-casing the letters). This can be done via list comprehension, which creates a new list. Or you could use a generator expression, which can be directly passed to the set constructor without first creating a temporary list:

result = set(s.lower() for s in the_list)

And lastly, Python has special syntactic sugar for this construct, using set comprehension, which is shown in mkrieger1’s answer.

user_19680
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