python - How to reference the empty string key in the Format String Syntax? -

the empty string ('') pertectly valid key dictionary, can not reference using format string syntax

data = { 'a' : 'hello' , '' : 'bye' } print '{a:<14s}'.format(**data) print '{:<14s}'.format(**data) 

which outputs:

hello          traceback (most recent call last):   file "xxx.py", line 3, in <module>     print '{:<14s}'.format(**data) indexerror: tuple index out of range 

is there way of referencing key ... dictionary key! can not convert data tuples; bit of background: doing auto-formatting based on generic format spec gets converted format string syntax using dicts data formatting. is, can not this:

print '{0:<14s}'.format(data['']) 

the data must passed format **data (basically, because doing generic .format(**data) in formatter class)

you can't use empty string. format strictly limits keys valid python identifiers, means have have @ least 1 letter or underscore @ start.

from grammar in format string syntax documentation:

replacement_field ::=  "{" [field_name] ["!" conversion] [":" format_spec] "}" field_name        ::=  arg_name ("." attribute_name | "[" element_index "]")* arg_name          ::=  [identifier | integer] 

so field_name either integer or valid python identifier.

note empty strings not stings not valid identifiers; cannot use strings spaces in either, or strings start digit. such strings can used in dictionary, not keyword arguments in python code nor field names in string formats.