How to get only positive numbers in python

Question

I want to get only positive numbers in python .

and if the user enter a negative number the program show an error message .

should I code lots of conditions like

if this : do this

if that : do that

and so on .

or is there another way for this ?

Can you share the code you've written so far in attempt to solve this problem, and point out the part that's not working? — Green Cloak Guy, Jun 09 '21 at 14:11
You should at least show your attempt that uses "lots of if function" — Sayse, Jun 09 '21 at 14:12

Andrea Nicolai · Answer 1 · 2021-06-09T14:15:12.633

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Use abs(x) Python native function.

EDIT: if you want to raise an error, instead, I would make use of assertions (example taken from here:

x = 0
assert x > 0, 'Only positive numbers are allowed'
print('x is a positive number.')

edited Jun 09 '21 at 14:15

answered Jun 09 '21 at 14:11

Andrea Nicolai

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3
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This will not show an error message if `x` is negative. It will simply convert `x` to a positive number the same distance from zero, which may not be what OP wants. – Green Cloak Guy Jun 09 '21 at 14:12
I think you're right. I would use an assertion then: – Andrea Nicolai Jun 09 '21 at 14:13

score 0 · Answer 2 · answered Jun 09 '21 at 14:14

You can use just an if statement like the code below:

n = float(input("Enter a positive number: "))
if num <= 0:
    raise ValueError("Please enter only positive numbers")

If the number is not a positive one you can manage as you prefer. In the example I put a raise, but you can also use a print statement with the message or an assertion.

score 0 · Answer 3 · answered Jun 09 '21 at 14:15

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Not sur to understand your question,

you only need to do if x >= 0: if you want to check if x is positive or negative

answered Jun 09 '21 at 14:15

PierreLouisNicolas

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score 0 · Answer 4 · answered Jun 09 '21 at 14:15

Simple options to achieve this can be

if input_num < 0
if abs(input_num) == input_num
In 1st case, you check if given number is less than 0 (it is negative)
In 2nd case, you use abs() function which gives a positive number from a negative or positive number. e.g. abs(-2) # returns 2

How to get only positive numbers in python

4 Answers4