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| """ | |
| A few practical conventions common to all printers. | |
| """ | |
| import re | |
| from collections.abc import Iterable | |
| from sympy.core.function import Derivative | |
| _name_with_digits_p = re.compile(r'^([^\W\d_]+)(\d+)$', re.U) | |
| 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. | |
| Examples | |
| ======== | |
| >>> 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']) | |
| """ | |
| if not text: | |
| return text, [], [] | |
| 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 = _name_with_digits_p.match(name) | |
| if m: | |
| 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 do not have | |
| free variables. In that case, check its variable list explicitly to | |
| get the context of the expression. | |
| """ | |
| if isinstance(expr, Derivative): | |
| return requires_partial(expr.expr) | |
| if not isinstance(expr.free_symbols, Iterable): | |
| return len(set(expr.variables)) > 1 | |
| return sum(not s.is_integer for s in expr.free_symbols) > 1 | |