True/False gotcha Python vs Ruby vs PowerShell vs NodeJS vs PHP

Evaluation of conditions is very important part programming. True is ture, false is false…

Or not? It might surprise you, but not all languages evaluate numbers, empty strings or empty arrays in the same way.

Let’s examine several technologies. Python, Ruby, PowerShell, NodeJS and PHP.

Here is small code written in Python:

def test(value):
    if value:
        print "True"
    else:
        print "False"

test(0)
test(1)
test("")
test([])
test({})

Here is similar code written in Ruby:

def test(value)
    if value
        print "True"
    else
        print "False"
    end
end

test(0)
test(1)
test("")
test([])
test({})

Let’s compare it to PowerShell:

Function Test($value) {
    if ($value) {
        Write-Host "True"
    } else {
        Write-Host "False"
    }
}

Test(0)
Test(1)
Test("")
Test(@())
Test(@{})

Same logic in JavaScript for NodeJS:

function test(value) {
    if (value) {
        console.log("True");
    } else {
        console.log("False");
    }
}

test(0);
test(1);
test("");
test([]);
test({});

Code in PHP:

<?php 
function test($value) {
    if ($value) {
        echo "True";
    } else {
        echo "False";
    }
}

test(0);
test(1);
test("");
test(array());
test(array());
?>

Results are little bit surprising:

 

	Python	Ruby	PowerShell	NodeJS	PHP
0	False	True	False	False	False
1	True	True	True	True	True
“”	False	True	False	False	False
[]	False	True	True	True	False
{}	False	True	True	True	False