Source code for sympy.printing.conventions

"""
A few practical conventions common to all printers.
"""


import re


[docs]def split_super_sub(text): """Split a symbol name into a name, superscripts and subscripts The first part of the symbol name is considered to be its actual 'name', followed by super- and subscripts. Each superscript is preceded with a "^" character or by "__". Each subscript is preceded by a "_" character. The three return values are the actual name, a list with superscripts and a list with subscripts. >>> from sympy.printing.conventions import split_super_sub >>> split_super_sub('a_x^1') ('a', ['1'], ['x']) >>> split_super_sub('var_sub1__sup_sub2') ('var', ['sup'], ['sub1', 'sub2']) """ pos = 0 name = None supers = [] subs = [] while pos < len(text): start = pos+1 if text[pos:pos+2] == "__": start += 1 pos_hat = text.find("^", start) if pos_hat < 0: pos_hat = len(text) pos_usc = text.find("_", start) if pos_usc < 0: pos_usc = len(text) pos_next = min(pos_hat, pos_usc) part = text[pos:pos_next] pos = pos_next if name is None: name = part elif part.startswith("^"): supers.append(part[1:]) elif part.startswith("__"): supers.append(part[2:]) elif part.startswith("_"): subs.append(part[1:]) else: raise RuntimeError("This should never happen.") # make a little exception when a name ends with digits, i.e. treat them # as a subscript too. m = re.match('(^[a-zA-Z]+)([0-9]+)$', name) if m is not None: name, sub = m.groups() subs.insert(0, sub) return name, supers, subs