Question

I’m creating a jQuery function on-the-fly with python:

jQuery = ("$('%(other_id)').click(function() { "
              "    if ($(this).is(':checked')) { "
              "        $('%(text_id)').show()     "
              "    } "
              "    else {"
              "       $('%(text_id)').hide()"
              "    }"
              " });")

I have to insert varibles into other_id and text_id. I see that $ sign is used for string templates (don’t know what it does though) So I escape them with double-$s($$)

jQuery = ("$$('%(other_id)').click(function() { "
              "    if ($$(this).is(':checked')) { "
              "        $$('%(text_id)').show()     "
              "    } "
              "    else {"
              "       $$('%(text_id)').hide()"
              "    }"
              " });")

However I can’t still format this:

>>> choice_id = 'foo'
>>> text_choice_id = 'bar'
>>> jQuery = ("$$('%(other_id)').click(function() { "
                  "    if ($$(this).is(':checked')) { "
                  "        $$('%(text_id)').show()     "
                  "    } "
                  "    else {"
                  "       $$('%(text_id)').hide()"
                  "    }"
                  " });")
>>> jQuery %{'other_id' : choice_id, 'text_id' : text_choice_id }

Traceback (most recent call last):
  File "<pyshell#123>", line 1, in <module>
    jQuery %{'other_id' : choice_id, 'text_id' : text_choice_id }
ValueError: unsupported format character ''' (0x27) at index 15

after escaping single-quotes:

>>> jQuery = ("$$(\'%(other_id)\').click(function() { "
                  "    if ($$(this).is(\':checked\')) { "
                  "        $$(\'%(text_id)\').show()     "
                  "    } "
                  "    else {"
                  "       $$(\'%(text_id)\').hide()"
                  "    }"
                  " });")
>>> jQuery %{'other_id' : choice_id, 'text_id' : text_choice_id }

Traceback (most recent call last):
  File "<pyshell#125>", line 1, in <module>
    jQuery %{'other_id' : choice_id, 'text_id' : text_choice_id }
ValueError: unsupported format character ''' (0x27) at index 15

can’t try string.format() because I have brackets inside the string. why am I keep getting ' as some unsupported format character?

Answer 1

You are missing the formatter type:

%(other_id)s

Note the s after the parenthesis; you want to interpolate the values as strings. Here is a working version instead:

jQuery = ("$('#%(other_id)s').click(function() { "
                  "    if ($(this).is(':checked')) { "
                  "        $('#%(text_id)s').show()     "
                  "    } "
                  "    else {"
                  "       $('#%(text_id)s').hide()"
                  "    }"
                  " });")

Dollar symbols have no meaning in %-style string formats and I’ve added the # id selectors for you. 🙂

Personally, I would use """ triple-quotes instead:

jQuery = """\
$('#%{other_id}s').click(function() {
    if ($(this).is(':checked')) {
        $('#%(text_id)s').show()
    }
    else {
        $('#%(text_id)s').hide()
    }
});
"""

Better still, put this into a Jinja template anyway (since you are using Flask) and render that instead:

jquery = render_template('toggle_field.js', other_id=choice_id, text_id=text_choice_id)

where toggle_field.js is the Jinja template version of the jQuery snippet:

$('#{{ other_id }}').click(function() {
    if ($(this).is(':checked')) {
        $('#{{ text_id }}').show()
    }
    else {
        $('#{{ text_id }}').hide()
    }
});