Check if object is a number or boolean

Question

Design a logical expression equivalent to the following statement:

x is a list of three or five elements, the second element of which is
the string 'Hip' and the first of which is not a number or Boolean.

What I have:

x = ['Head', 'Hip', 10]
print x[1] is 'Hip'

My question: How do you check for whether or not it is a Boolean or a number?

Asked By: Joakim

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Source

Answer 1

To answer the specific question:

isinstance(x[0], (int, float))

This checks if x[0] is an instance of any of the types in the tuple (int, float).

You can add bool in there, too, but it’s not necessary, because bool is itself a subclass of int.

Doc reference:

To comment on your current code, you shouldn’t rely on interning of short strings. You are supposed to compare strings with the == operator:

x[1] == 'Hip'

Answered By: Lev Levitsky

Answer 2

Python 2

import types

x = False
print(type(x) == types.BooleanType) # True

Python 3

# No need to import types module
x = False
print(type(x) == bool) # True

Answered By: Peyman Karimi

Answer 3

Easiest i would say:

type(x) == type(True)

Answered By: CurlyMo

Answer 4

In python3 this would be: type(x)==bool see example.

Answered By: Thijs Cobben

Answer 5

You should compare the type of x to the bool class:

type(x) == bool

or:

type(x) == type(True)

Here is more on the type method

From Data model docs:

Booleans (bool)

These represent the truth values False and True. The two objects representing the values False and True are the only Boolean objects. The Boolean type is a subtype of the integer type, and Boolean values behave like the values 0 and 1, respectively, in almost all contexts, the exception being that when converted to a string, the strings "False" or "True" are returned, respectively.

Answered By: Justin Golden

Answer 6

I follow the recent answer who tell to use type and it seems to be the incorrect way according to pylint validation:

I got the message:

C0123: Using type() instead of isinstance() for a typecheck.
(unidiomatic-typecheck)

Even if it’s an old answer, the correct one is the accepted answer of @Lev Levitsky:

isinstance(x[0], (int, float))

Answered By: Michael

Answer 7

I like to keep it simple to read..
This will accept bool, string, number and read it to a bool

def var2bool(v):
if type(v) == type(True):
    res = v
elif type(v) == type(0):
    if v == 0:
        res = False
    else:
        res = True
elif v.lower() in ("yes", "true", "t", "1"):
    res = True
else:
    res = False
return res

Answered By: James Gardiner

Answer 8

Python 3:

Use assert to check is some statement is True or False. If False, it will raise an AssertionError.

assert(isinstance(x[0], (int, float)))

You can then catch the error like that:

except AssertionError as error:
    print(error)
    # do stuff...

Answered By: Onyr

Check if object is a number or boolean

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