def elements(all_isotopes=True):
el = pd.read_pickle(pkgrs.resource_filename('<STR_LIT>', '<STR_LIT>'))<EOL>if all_isotopes:<EOL><INDENT>return el.set_index('<STR_LIT>')<EOL><DEDENT>else:<EOL><INDENT>def wmean(g):<EOL><INDENT>return (g.atomic_weight * g.percent).sum() / <NUM_LIT:100><EOL><DEDENT>iel = el.groupby('<STR_LIT>').apply(wmean)<EOL>iel.name = '<STR_LIT>'<EOL>return iel<EOL><DEDENT>
Loads a DataFrame of all elements and isotopes.

Scraped from https://www.webelements.com/

Returns
-------
pandas DataFrame with columns (element, atomic_number, isotope, atomic_weight, percent)