I need to format a long line involving quite a some vars so I'm using the mapping key style formatting. (And personally I don't like `str.format()`. :)

I tried a lot but failed to find out what the correct syntax should be.

---

With a tuple param it works fine:

```none
>>> width = 6
>>> num = 123
>>>
>>> '%0*d' % (width, num)
'000123'

```

I failed to figure out how to do it with a dict param:

```none
>>> '%(width)0*d' % dict(width=width, num=num)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: not enough arguments for format string
>>>
>>> '%(width)(num)0*d' % dict(width=width, num=num)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: unsupported format character '(' (0x28) at index 8
>>>
>>> '%(width)0*(num)d' % dict(width=width, num=num)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: not enough arguments for format string

```

For now I'm using some workaround. Just curious if this is possible or it's not supported at all.