How do I use string formatting with explicit character escape codes in Python?

You are looking for the unichr() function:

s = u'{}'.format(unichr(i))

or just plain

s = unichr(i)

unichr(integer) produces a unicode character for the given codepoint.

The \uxxxx syntax only works for string literals; these are processed by the Python compiler before running the code.

Demo:

>>> for i in range(0x2550, 0x257F):
...     print unichr(i)
... 
═
║
╒
╓
╔
╕
╖
# etc.

If you ever do have literal \uxxxx sequences in your strings, you can still have Python turn those into Unicode characters with the unicode_escape codec:

>>> print u'\\u2550'
\u2550
>>> print u'\\u2550'.decode('unicode_escape')
═
>>> print '\\u2550'.decode('unicode_escape')
═
>>> '\\u2550'.decode('unicode_escape')
u'\u2550'

In Python 2, you can use this codec on both byte string and unicode string values; the output is always a unicode string.