Woocommerce add to simple product attribute programmatically [closed]

i want to create a function which will add to specific products an attribute programmatically.
i use the below code but it doesnt seem to work.

 $attributedata = Array(
     'pa_color'=>Array( 
           'name'=>'pa_color', 
           'value'=>'black',
           'is_visible' => '1',
           'is_taxonomy' => '1'
     )
);

    update_post_meta( $productID,'_product_attributes',$attributedata );

if i set taxonomy to 0 the attribute is passed to the product but it doesnt appear in the front end unless i press update manually to each product.
what can i do to add attributes to product?
i want to mention that the products are simple products not variable.

wp_set_object_terms( $productID, 'black', 'pa_color', true );

$att_color = Array('pa_color' =>Array(
       'name'=>'pa_color',
       'value'=>'black',
       'is_visible' => '1',
       'is_taxonomy' => '1'
     ));

update_post_meta( $productID, '_product_attributes', $att_color);