converting a single integer number input to a list in python

Question

I am looking for a single line command in python to convert an integer input to list. The following is the situation.

mylist=[]
mylist=list(input('Enter the numbers: '))

The above line works perfectly if i give more than one number as input. Eg 1,2,3 . But it gives Error when i give only a single digit entry. Eg: 1 . Saying it cannot convert an integer to list. I don't want to run a loop asking user for each input. So i want a one line command which will work for one or more digits input given by user separated by commas.

Thanking you, -indiajoe

Renato · Accepted Answer · 2012-01-20 18:45:00Z

3

I think that the simplest thing that you can do is:

mylist = map(int, raw_input('Enter the numbers: ').split(','))

But it's nearly the same that using a list comprehension.

answered Jan 20, 2012 at 18:45

Renato

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Comments

Rik Poggi · Accepted Answer · 2012-01-20 18:38:35Z

3

You should use raw_input and convert to int with a list comprehension:

user_input = raw_input('Enter the numbers: ')
my_list = [int(i) for i in user_input.split(',')]

From the offical documentation: raw_input reads a line from input, converts it to a string (stripping a trailing newline), and returns that.

edited Jan 20, 2012 at 18:38

answered Jan 20, 2012 at 18:25

Rik Poggi

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5 Comments

SRC Over a year ago

You can also use eval to convert your string list to int: mylist = map(eval, mylist)

indiajoe Over a year ago

Thanks, but i was trying to precisely avoid this loop. Isn't there any one liner for this common use? If not, I shall go ahead with this loop method.

Rik Poggi Over a year ago

@SRC: It's a bad practice to use eval on a user input! You should do that only if really needed and with the necessary check.

Rik Poggi Over a year ago

@indiajoe: You will have the loop anyway, could be hidden inside map but there will be anyway! Given so, to choose between a list comprehension or map (or filter etc...) is mearly a matter of taste. Nevertheless you should be aware that in python-3 map is a generator expression so in case one day you'll find yourself porting your own code just remember to wrap map with list (if you need a list and not a generator), like list(map(...)).

indiajoe Over a year ago

@RikPoggi: Thanks for the info regd the python 3.

jrennie · Accepted Answer · 2012-01-20 18:32:34Z

1

input eval()'s what you type. So, when you type 1,2,3, the result is a tuple; when you type 1, the result is an int. Try typing 1, instead of 1. Note that your first line (mylist=[]) is unnecessary.

answered Jan 20, 2012 at 18:32

jrennie

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2 Comments

indiajoe Over a year ago

Yes, typing a comma after integer works. Eg: 1, But looks a little untidy to ask a user to put extra comma. Or I will have to add a try: except: block to catch it and correct.

Renato Over a year ago

Following this approach, this will work: mylist=list(eval(raw_input('Enter the numbers: ')+',')). (Doing the eval with raw_input and the comma).

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