Question

I am trying to convert this php function

function strpos_r($haystack, $needle)
{
    if(strlen($needle) > strlen($haystack))
        trigger_error(sprintf("%s: length of argument 2 must be <= argument 1", __FUNCTION__), E_USER_WARNING);

    $seeks = array();
    while($seek = strrpos($haystack, $needle))
    {
        array_push($seeks, $seek);
        $haystack = substr($haystack, 0, $seek);
    }
    return $seeks;
}

I have written this python function, but is not working as expected.

def strposR(haystack, needle):
    if strlen(needle) > strlen(haystack):
        sys.stderr.write("length of argument 2 must be <= argument 1")
    seeks = []
    seek = 0
    while seek == haystack.rfind(needle):
        seeks.append(seek)
        haystack = haystack[0:seek]
    return seeks
def strlen(x):
    return len(x)

What I am doing wrong? Any pointers will be much appreciated.

Answer 1

This works for me:

def strpos_r(haystack, needle):
    positions = []
    position = haystack.rfind(needle)

    while position != -1:
        positions.append(position)
        haystack = haystack[:position]
        position = haystack.rfind(needle)

    return positions

Also, functions should not really handle input errors for you. You usually just return False or let the function throw an execution error.