unit_object.py 文件源码

def get_latex_representation(expr, registry):
    symbol_table = {}
    for ex in expr.free_symbols:
        try:
            symbol_table[ex] = registry.lut[str(ex)][3]
        except:
            symbol_table[ex] = r"\rm{" + str(ex).replace('_', '\ ') + "}"

    # invert the symbol table dict to look for keys with identical values
    invert_symbols = {}
    for key, value in symbol_table.items():
        if value not in invert_symbols:
            invert_symbols[value] = [key]
        else:
            invert_symbols[value].append(key)

    # if there are any units with identical latex representations, substitute
    # units to avoid  uncanceled terms in the final latex expression.
    for val in invert_symbols:
        symbols = invert_symbols[val]
        for i in range(1, len(symbols)):
            expr = expr.subs(symbols[i], symbols[0])
    prefix = None
    if isinstance(expr, Mul):
        coeffs = expr.as_coeff_Mul()
        if coeffs[0] == 1 or not isinstance(coeffs[0], Float):
            pass
        else:
            expr = coeffs[1]
            prefix = Float(coeffs[0], 2)
    latex_repr = latex(expr, symbol_names=symbol_table, mul_symbol="dot",
                       fold_frac_powers=True, fold_short_frac=True)

    if prefix is not None:
        latex_repr = latex(prefix, mul_symbol="times") + '\\ ' + latex_repr

    if latex_repr == '1':
        return ''
    else:
        return latex_repr