Check if value is zero or not null in python

Question

Often I am checking if a number variable number has a value with if number but sometimes the number could be zero. So I solve this by if number or number == 0.

Can I do this in a smarter way? I think it's a bit ugly to check if value is zero separately.

Edit

I think I could just check if the value is a number with

def is_number(s):
    try:
        int(s)
        return True
    except ValueError:
        return False

but then I will still need to check with if number and is_number(number).

Your title asks for `not None` or a number. Are you saying you have multiple types now? — Martijn Pieters, Jan 29 '15 at 08:32
Your `is_number()` test will work for strings with values convertible to integers. That's something entirely different. — Martijn Pieters, Jan 29 '15 at 08:33
See also [What is the most pythonic way to check if an object is a number?](https://stackoverflow.com/a/46324571/562769) — Martin Thoma, Sep 25 '17 at 13:03

Martijn Pieters · Accepted Answer · 2015-01-29T08:36:19.670

75

If number could be None or a number, and you wanted to include 0, filter on None instead:

if number is not None:

If number can be any number of types, test for the type; you can test for just int or a combination of types with a tuple:

if isinstance(number, int):  # it is an integer
if isinstance(number, (int, float)):  # it is an integer or a float

or perhaps:

from numbers import Number

if isinstance(number, Number):

to allow for integers, floats, complex numbers, Decimal and Fraction objects.

edited Jan 29 '15 at 08:36

answered Jan 29 '15 at 08:29

Martijn Pieters

1,048,767
296
4,058
3,343

1

But I do want my statement to evaluate as true if the value is not null OR the value is zero. – Jamgreen Jan 29 '15 at 08:30
Of course. Thank you.. What if I'm only interested in knowing if it is a number? I've edited my question – Jamgreen Jan 29 '15 at 08:33
@Jamgreen: then test for the **type** with `isinstance()`. – Martijn Pieters Jan 29 '15 at 08:33
@MartijnPieters How do you get isinstance method? – Sam Kah Chiin Nov 26 '20 at 02:57
@SamKahChiin: it isn't a method. It's a [built-in function](https://docs.python.org/3/library/functions.html#isinstance). – Martijn Pieters Nov 26 '20 at 09:35

score 17 · Answer 2 · answered Jan 29 '15 at 08:39

17

Zero and None both treated as same for if block, below code should work fine.

if number or number==0:
    return True

answered Jan 29 '15 at 08:39

Amey Jadiye

3,066
3
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38

score 2 · Answer 3 · answered Oct 28 '17 at 14:57

2

The simpler way:

h = ''
i = None
j = 0
k = 1
print h or i or j or k

Will print 1

print k or j or i or h

Will print 1

answered Oct 28 '17 at 14:57

Luciano Pinheiro

85
4

score 1 · Answer 4 · answered Jun 05 '22 at 14:49

DO NOT USE:

if number or number == 0:
    return true

this will check "number == 0" even if it is None. You can check for None and if it's value is 0:

if number and number == 0:
    return true

Python checks the conditions from left to right: https://docs.python.org/3/reference/expressions.html#evaluation-order

score 0 · Answer 5 · answered Jun 28 '17 at 07:43

You can check if it can be converted to decimal. If yes, then its a number

from decimal import Decimal

def is_number(value):
    try:
        value = Decimal(value)
        return True
    except:
        return False

print is_number(None)   // False
print is_number(0)      // True
print is_number(2.3)    // True
print is_number('2.3')  // True (caveat!)

Check if value is zero or not null in python

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5 Answers5

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