89 lines
2.5 KiB
Python
89 lines
2.5 KiB
Python
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"""
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A few practical conventions common to all printers.
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"""
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import re
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from collections.abc import Iterable
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from sympy.core.function import Derivative
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_name_with_digits_p = re.compile(r'^([^\W\d_]+)(\d+)$', re.U)
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def split_super_sub(text):
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"""Split a symbol name into a name, superscripts and subscripts
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The first part of the symbol name is considered to be its actual
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'name', followed by super- and subscripts. Each superscript is
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preceded with a "^" character or by "__". Each subscript is preceded
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by a "_" character. The three return values are the actual name, a
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list with superscripts and a list with subscripts.
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Examples
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========
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>>> from sympy.printing.conventions import split_super_sub
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>>> split_super_sub('a_x^1')
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('a', ['1'], ['x'])
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>>> split_super_sub('var_sub1__sup_sub2')
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('var', ['sup'], ['sub1', 'sub2'])
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"""
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if not text:
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return text, [], []
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pos = 0
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name = None
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supers = []
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subs = []
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while pos < len(text):
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start = pos + 1
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if text[pos:pos + 2] == "__":
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start += 1
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pos_hat = text.find("^", start)
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if pos_hat < 0:
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pos_hat = len(text)
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pos_usc = text.find("_", start)
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if pos_usc < 0:
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pos_usc = len(text)
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pos_next = min(pos_hat, pos_usc)
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part = text[pos:pos_next]
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pos = pos_next
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if name is None:
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name = part
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elif part.startswith("^"):
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supers.append(part[1:])
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elif part.startswith("__"):
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supers.append(part[2:])
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elif part.startswith("_"):
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subs.append(part[1:])
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else:
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raise RuntimeError("This should never happen.")
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# Make a little exception when a name ends with digits, i.e. treat them
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# as a subscript too.
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m = _name_with_digits_p.match(name)
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if m:
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name, sub = m.groups()
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subs.insert(0, sub)
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return name, supers, subs
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def requires_partial(expr):
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"""Return whether a partial derivative symbol is required for printing
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This requires checking how many free variables there are,
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filtering out the ones that are integers. Some expressions do not have
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free variables. In that case, check its variable list explicitly to
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get the context of the expression.
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"""
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if isinstance(expr, Derivative):
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return requires_partial(expr.expr)
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if not isinstance(expr.free_symbols, Iterable):
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return len(set(expr.variables)) > 1
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return sum(not s.is_integer for s in expr.free_symbols) > 1
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