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
def requires_partial(expr): """Return whether a partial derivative symbol is required for printing This requires checking how many free variables there are, filtering out the ones that are integers. Some expressions don't have free variables. In that case, check its variable list explicitly to get the context of the expression. """ ## checking for the attribute '__iter__' is Python 2.5 friendly. ## For 2.6+, say isinstance(expr.free_symbols, collections.Iterable) if not hasattr(expr.free_symbols, '__iter__'): return len(set(expr.variables)) > 1 return sum(not s.is_integer for s in expr.free_symbols) > 1