how to convert a string boolean into an IF statement in Python

Question

I am trying to create a more complicated boolean function that I'll use between functions. Here is the simplified problem:

a = "1 == 2"

if a:
    print ("it is not working")
else:
    print ("it worked")

Out[1]:

it is not working

Basically I am trying to pass a function as a string and use that in a boolean later on but it turns out as True always.

I also tried:

bool(a)

Out[1]: True

"1 == 2" is a string... And any string that is not empty is 'truthy' in python... So that's why its always returning true... If you want 1 == 2 to be evaluated as a Boolean, remove the quotation marks around — Jordan Simba
– Jordan Simba, Commented Dec 25, 2019 at 20:58
a string is always true if its not None. This sounds like an XY problem. Normally its alwyas discouraged an approach like this where you want to eval a string. However if your insistant on it you should look up ast.literal_eval — Chris Doyle
– Chris Doyle, Commented Dec 25, 2019 at 20:58
@JordanSimba yeah sorry thats what i mean, string is always true unless its empty. — Chris Doyle
– Chris Doyle, Commented Dec 25, 2019 at 21:02
Try eval(a). For a = "1 == 2", eval(a) = False. For a = "1 == 1", eval(a) = True. More info on eval — DarrylG
– DarrylG, Commented Dec 25, 2019 at 21:11

DarrylG · Accepted Answer · 2019-12-26 13:01:01Z

1

a = "1 == 2"
eval(a)
>>>False

a = "1 == 1"
eval(a) 
>>> True

answered Dec 26, 2019 at 13:01

DarrylG

17.2k2 gold badges20 silver badges25 bronze badges

Sign up to request clarification or add additional context in comments.

1 Answer 1