Why do empty string and None evaluate differently? [duplicate]

Question

Why do those two evaluate differently?

In [34]: a = ''

In [35]: if a or a >=0:
    print 'y'
    ....:     
y

In [36]: a = None

In [37]: if a or a >=0:
    print 'y'
    ....:

I thought an empty string also evaluates to None (I know they are not the same)? Or is it just falsy and thus evaluates to 0 (which then evaluates to None if tested like if a: do something)?

I missed where you get confused. In the first example? It print y because of the >= 0 part. — keyser
– keyser, Commented May 7, 2014 at 7:38
It's because of how string vs int comparison works. The if a part doesn't kick in because, as you say, an empty string and None is not the same thing. — keyser
– keyser, Commented May 7, 2014 at 7:40
Even more related. The short answer is: why would you ever want to do such a comparison? It's even fixed in python 3 — keyser
– keyser, Commented May 7, 2014 at 7:42

Kirill Zaitsev · Accepted Answer · 2014-05-07 09:25:10Z

0

It's because in CPython int comes before string

from docs:

CPython implementation detail: Objects of different types except numbers are ordered by their type names; objects of the same types that don’t support proper comparison are ordered by their address.

so:

>>> '1' > 1
True

answered May 7, 2014 at 9:25

Kirill Zaitsev

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