def find(sub=None, disp=False):
if sub is None:<EOL><INDENT>result = list(_current_constants.keys())<EOL><DEDENT>else:<EOL><INDENT>result = [key for key in _current_constants<EOL>if sub.lower() in key.lower()]<EOL><DEDENT>result.sort()<EOL>if disp:<EOL><INDENT>for key in result:<EOL><INDENT>print(key)<EOL><DEDENT>return<EOL><DEDENT>else:<EOL><INDENT>return result<EOL><DEDENT>
Return list of codata.physical_constant keys containing a given string.

Parameters
----------
sub : str, unicode
    Sub-string to search keys for.  By default, return all keys.
disp : bool
    If True, print the keys that are found, and return None.
    Otherwise, return the list of keys without printing anything.

Returns
-------
keys : list or None
    If `disp` is False, the list of keys is returned.
    Otherwise, None is returned.

See Also
--------
codata : Contains the description of `physical_constants`, which, as a
    dictionary literal object, does not itself possess a docstring.