Sort an integer list in Python

Question

I'm a beginner programmer and I'm trying to make an exercise.

I want to sort an integer list, but every time I run my code, the list is not sorted. I've tried it in a couple of different ways with sorted() or .sort(), but nothing seems to help.

def main():

    _list1_ = []
    _list2_ = []

    print("Enter random numbers and enter Q to quit: ")
    userInput1 = input("")
    while userInput1.upper() != "Q":
        _list1_.append(int(userInput1))
        userInput1 = input("")

    print("Enter random numbers and enter Q to quit:")
    userInput2 = input("")
    while userInput2.upper() != "Q":
        _list2_.append(int(userInput2))
        userInput2 = input("")

    sorted(_list1_)
    sorted(_list2_)

    print(_list1_)

main()

(This was the top search engine hit (DDG) for "how to sort list of integers in Python" (used in the 2023 blog post "Ask like a human: Implementing semantic search on Stack Overflow")... It is an example of the typical low-scored duplicates in search engine results.) — Peter Mortensen
– Peter Mortensen, Commented Jul 31, 2023 at 19:57
For that, something like How to sort a list of strings numerically (2010), Sort a list of numerical strings in ascending order (2012), and How to sort a Python list of strings of numbers (2013). Though there must be a canonical from 2008 or 2009. — Peter Mortensen
– Peter Mortensen, Commented Jul 31, 2023 at 21:28

Tonechas · Accepted Answer · 2017-01-07 01:32:26Z

9

sorted() doesn't sort the list in place. It returns the sorted list, so you will need to change the 2 sorted() calls to something like this:

_list1_ = sorted(_list1_)
_list2_ = sorted(_list2_)

It's always a good idea to read the documentation to get an understanding for how the functions work. Here is the docs for sorted https://docs.python.org/2/library/functions.html#sorted

edited Jan 7, 2017 at 1:32

Tonechas

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answered Apr 3, 2016 at 13:53

Sendoa

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2 Comments

idjaw Over a year ago

_list_1.sort() and _list2_.sort() will do it in place. Good to mention that.

saeedgnu Over a year ago

Specially because sorted allocates a new list, so it takes extra memory.

Mark Skelton · Accepted Answer · 2016-04-03 14:04:01Z

sorted returns the sorted list whereas sort performs the sort in place.

So you could either do:

_list1_ = sorted(_list_)

or:

_list1_.sort()

If you were to use sort (my preferred method) your code would look like this:

def main():

    _list1_ = []
    _list2_ = []

    print("Enter random numbers and enter Q to quit: ")
    userInput1 = input("")
    while userInput1.upper() != "Q":
        _list1_.append(int(userInput1))
        userInput1 = input("")

    print("Enter random numbers and enter Q to quit:")
    userInput2 = input("")
    while userInput2.upper() != "Q":
        _list2_.append(int(userInput2))
        userInput2 = input("")

    _list1_.sort()
    _list2_.sort()

    print(_list1_)

main()

Eular · Accepted Answer · 2016-04-03 13:57:01Z

0

sorted(_list1_)

returns a list after sorting list1, It does not sort the list1. so write

print(sorted(_list1_))

or assign the sorted list1 to list1, like

_list1_ = sorted(_list1_)

answered Apr 3, 2016 at 13:57

Eular

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