def round_expr(self, expr: sympy.Expr, num_digits: int) -> sympy.Expr:
"""
Rounds all the numbers in a SymPy expression. This is useful for pretty-printing.
:param expr: SymPy expression to round.
:param num_digits: number of digits to leave.
:return: expression with rounded numbers.
"""
return expr.xreplace(
{n: round(n, num_digits)
for n in expr.atoms(sympy.Number)})
def substitute_indexed_symbols(expression: sp.Expr) -> sp.Expr:
"""Substitute `~sympy.tensor.indexed.IndexedBase` with symbols.
See :doc:`compwa-org:report/008` for more info.
"""
return expression.xreplace(
{
s: _indexed_to_symbol(s)
for s in expression.free_symbols
if isinstance(s, sp.Indexed)
}
)
def rename_symbols(
expression: sp.Expr, renames: Union[Callable[[str], str], Dict[str, str]]
) -> sp.Expr:
r"""Rename symbols in an expression.
>>> a, b, x = sp.symbols(R"a \beta x")
>>> expr = a + b * x
>>> rename_symbols(expr, renames={"a": "A", R"\beta": "B"})
A + B*x
>>> rename_symbols(expr, renames=lambda s: s.replace("\\", ""))
a + beta*x
>>> rename_symbols(expr, renames={"non-existent": "c"})
Traceback (most recent call last):
...
KeyError: "No symbol with name 'non-existent' in expression"
"""
substitutions: Dict[sp.Symbol, sp.Symbol] = {}
if callable(renames):
for old_symbol in expression.free_symbols:
new_name = renames(old_symbol.name)
new_symbol = sp.Symbol(new_name, **old_symbol.assumptions0)
substitutions[old_symbol] = new_symbol
elif isinstance(renames, dict):
for old_name, new_name in renames.items():
# pylint: disable=cell-var-from-loop
matches = filter(
lambda s: s.name == old_name, expression.free_symbols
)
try:
old_symbol = next(matches)
except StopIteration:
# pylint: disable=raise-missing-from
raise KeyError(
f"No symbol with name '{old_name}' in expression"
)
new_symbol = sp.Symbol(new_name, **old_symbol.assumptions0)
substitutions[old_symbol] = new_symbol
else:
raise TypeError(f"Cannot rename from type {type(renames).__name__}")
return expression.xreplace(substitutions)
def _round_sympy_expr(expr: sympy.Expr, num_digits: int = 4) -> sympy.Expr:
return expr.xreplace(
{n: round(n, num_digits)
for n in expr.atoms(sympy.Number)})
def _remove_residue_constants(expression: sp.Expr) -> sp.Expr:
residue_constants = filter(
lambda s: s.name.startswith(R"\gamma_"), expression.free_symbols
)
return expression.xreplace({gamma: 1 for gamma in residue_constants})
def round_expr(self, expr: sympy.Expr, num_digits: int) -> sympy.Expr:
return expr.xreplace(
{n: round(n, num_digits)
for n in expr.atoms(sympy.Number)})
