CODEWITHSUNDEEP
python
shuttle87
shuttle87

Reputation: 15934

Most idiomatic way of applying modulo to list in python

Currently I have a list with some non-repeating positive integers in it say a = [1,2,6,15,19]

What is the most idiomatic way to create a function that returns a new list that is the result of taking the modulo %x of each element of a without having any repeated elements in the output?

Specifically I want f(a,x) to return [1%x,2%x,6%x,15%x,19%x] without the repeated elements.

For example f([1,2,6,15,19],4) would return [1,2,3]

Upvotes: 2

Views: 5005

Answers (2)

Martijn Pieters
Martijn Pieters

Reputation: 1122392

Use a list comprehension, and a set() to filter out duplicates and preserve order:

def f(values, x):
    seen = set()
    add = seen.add
    return [res for res in (i % x for i in values) if res not in seen and not add(res)]

Demo:

>>> f([1,2,6,15,19], 4)
[1, 2, 3]

If order does not need to be preserved, just use a set comprehension instead and return the resulting set:

def f(values, x):
    return {i % x for i in values}

Upvotes: 6

Justin
Justin

Reputation: 43255

To return the list of the set you need a set comprehension wrapped in a list.

def f(l, x):
    return list({i % x for i in l})

As per question comments, returning the set may be the best option.

def f(l, x):
    return {i % x for in l}

Upvotes: 4

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