How to construct a set out of list items in python?

I have a list of filenames in python and I would want to construct a set out of all the filenames.

filelist=[]
for filename in filelist:
    set(filename)

This does not seem to work. How can do this?

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

If you have a list of hashable objects (filenames would probably be strings, so they should count):

lst = ['foo.py', 'bar.py', 'baz.py', 'qux.py', Ellipsis]

you can construct the set directly:

s = set(lst)

In fact, set will work this way with any iterable object! (Isn’t duck typing great?)

If you want to do it iteratively:

s = set()
for item in iterable:
    s.add(item)

But there’s rarely a need to do it this way. I only mention it because the set.add method is quite useful.

Method 2

The most direct solution is this:

s = set(filelist)

The issue in your original code is that the values weren’t being assigned to the set. Here’s the fixed-up version of your code:

s = set()
for filename in filelist:
    s.add(filename)
print(s)

Method 3

You can do

my_set = set(my_list)

or, in Python 3,

my_set = {*my_list}

to create a set from a list. Conversely, you can also do

my_list = list(my_set)

or, in Python 3,

my_list = [*my_set]

to create a list from a set.

Just note that the order of the elements in a list is generally lost when converting the list to a set since a set is inherently unordered. (One exception in CPython, though, seems to be if the list consists only of non-negative integers, but I assume this is a consequence of the implementation of sets in CPython and that this behavior can vary between different Python implementations.)

Method 4

Here is another solution:

>>>list1=["C:\","D:\","E:\","C:\"]
>>>set1=set(list1)
>>>set1
set(['E:\', 'D:\', 'C:\'])

In this code I have used the set method in order to turn it into a set and then it removed all duplicate values from the list

Method 5

Simply put the line:

new_list = set(your_list)

Method 6

One general way to construct set in iterative way like this:

aset = {e for e in alist}

Method 7

You can also use list comprehension to create set.

s = {i for i in range(5)}

Method 8

All the above answers are correct but if you want to preserve the order of your list you’ll need to proceed as follow

list(dict.fromkeys(your_list))

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0