How to convert numbers to a number list in python?

Question

Possible Duplicate:
How can I get a list as input from the user in Python?

I currently have this:

c = eval(input("Enter a group of numbers "))
#say someone types 123
print (c)
#prints out 123

I want this:

c = eval(input("Enter a group of numbers "))
#say they enter 123
print (c)
#prints out [1,2,3]

I want 123 to end up as [1,2,3]. How can I do that?

Do NOT use `eval`. Also, if you're using python 2, don't use `input`. Both will result in an arbitrary code execution vulnerability. — Colin Dunklau, Oct 03 '12 at 17:37
I know everyone likes easy rep, but for quality Q&A, common questions really need to be closed, not answered with a dozen identical answers every time. — Junuxx, Oct 03 '12 at 17:41

score 6 · Answer 1 · answered Oct 03 '12 at 17:34

6

In [32]: c=raw_input()
123

In [33]: map(int,c)
Out[33]: [1, 2, 3]

use split() if the input is something like 1 2 3:

In [37]: c=raw_input()
1 2 3

In [38]: map(int,c.split())
Out[38]: [1, 2, 3]

answered Oct 03 '12 at 17:34

Ashwini Chaudhary

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score 4 · Answer 2 · answered Oct 03 '12 at 17:35

4

You can convert the numbers into ints using map():

>>> map(int, '123')
[1, 2, 3]

answered Oct 03 '12 at 17:35

Blender

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score 4 · Answer 3 · answered Oct 03 '12 at 17:35

4

>>> s = '123'
>>> [int(c) for c in s]
[1, 2, 3]

answered Oct 03 '12 at 17:35

John Vinyard

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Netwave · Answer 4 · 2012-10-03T17:51:17.177

1

How about?:

c = [int(x) for x in input("Enter a group of numbers ")]
#list comprehension over the input function

Entering 123 the result is [1, 2, 3]

OK, lets say that for python 2.x (input returns an int object)

c = [int(x) for x in str(input("Enter a group of numbers "))]
#added an str() function for iterating

edited Oct 03 '12 at 17:51

answered Oct 03 '12 at 17:36

Netwave

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this won't work in python 2.x – Ashwini Chaudhary Oct 03 '12 at 17:38
@AshwiniChaudhary: It will. I just tested it with Python 2.6. – Blender Oct 03 '12 at 17:40
I'm happy it is usefull for you. – Netwave Oct 03 '12 at 17:43
1

@Blender No it won't, `input()` will return an integer in python 2.x, and the for loop will raise the error: `TypeError: 'int' object is not iterable` – Ashwini Chaudhary Oct 03 '12 at 17:44
@AshwiniChaudhary: My bad, I tested something a little bit different. – Blender Oct 03 '12 at 17:45
@Ashwini Chaudhary, You could just add an str() for the input, so it will work in python 2.x – Netwave Oct 03 '12 at 17:46
@user1717888 I wonder how this solution worked for you? – Ashwini Chaudhary Oct 03 '12 at 17:46

score 0 · Answer 5 · answered Oct 03 '12 at 17:36

0

You could convert it to a string, and then convert each character in the string into a number.


myStr = str(myInt)
out = [int(i) for i in myStr]

answered Oct 03 '12 at 17:36

BostonJohn

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score 0 · Answer 6 · answered Oct 03 '12 at 17:42

First of all, the following:

c = eval(input("Enter a group of numbers "))

Is the same as:

c = eval(eval(raw_input("Enter a group of numbers ")))

So you are calling eval twice now. More information on input can be found here.

This is a possible solution for what you want:

c = raw_input("Enter a group of numbers "))
c = [int(i) for i in c]
print(c)

You can of course reduce the above example to two lines (even one actually).

the wolf · Answer 7 · 2012-10-03T18:08:26.037

You should not use eval on user input generally. Someone can type a statement that will eval into mischief.

For the same reason, you should avoid the use of input() since it is the equivalent of eval(raw_input()) also can lead to mischief -- intended or not.

You can, however, SAFELY get Python interpretation of user input into Python data structures with ast.literal_eval:

>>> import ast
>>> ast.literal_eval(raw_input('Type Python input: '))
Type Python input: 1,2,3
(1, 2, 3)
>>> ast.literal_eval(raw_input('Type Python input: '))
Type Python input: [1,2,3]
[1, 2, 3]
>>> ast.literal_eval(raw_input('Type Python input: '))
Type Python input: 123
123
>>> ast.literal_eval(raw_input('type a number: '))
type a number: 0xab
171

(In each case, the first line after >>> Type Python input: is what I typed into the raw_input()

If you want to split digits apart, you can do this:

>>> [int(c) for c in raw_input() if c in '1234567890']
1234
[1, 2, 3, 4]
>>> [int(c) for c in raw_input() if c in '1234567890']
123a45
[1, 2, 3, 4, 5]

Notice the non digit is filtered.

How to convert numbers to a number list in python?

7 Answers7