Inzynierka/Lib/site-packages/pandas/core/computation/expr.py
2023-06-02 12:51:02 +02:00

841 lines
24 KiB
Python

"""
:func:`~pandas.eval` parsers.
"""
from __future__ import annotations
import ast
from functools import (
partial,
reduce,
)
from keyword import iskeyword
import tokenize
from typing import (
Callable,
TypeVar,
)
import numpy as np
from pandas.compat import PY39
from pandas.errors import UndefinedVariableError
import pandas.core.common as com
from pandas.core.computation.ops import (
ARITH_OPS_SYMS,
BOOL_OPS_SYMS,
CMP_OPS_SYMS,
LOCAL_TAG,
MATHOPS,
REDUCTIONS,
UNARY_OPS_SYMS,
BinOp,
Constant,
Div,
FuncNode,
Op,
Term,
UnaryOp,
is_term,
)
from pandas.core.computation.parsing import (
clean_backtick_quoted_toks,
tokenize_string,
)
from pandas.core.computation.scope import Scope
from pandas.io.formats import printing
def _rewrite_assign(tok: tuple[int, str]) -> tuple[int, str]:
"""
Rewrite the assignment operator for PyTables expressions that use ``=``
as a substitute for ``==``.
Parameters
----------
tok : tuple of int, str
ints correspond to the all caps constants in the tokenize module
Returns
-------
tuple of int, str
Either the input or token or the replacement values
"""
toknum, tokval = tok
return toknum, "==" if tokval == "=" else tokval
def _replace_booleans(tok: tuple[int, str]) -> tuple[int, str]:
"""
Replace ``&`` with ``and`` and ``|`` with ``or`` so that bitwise
precedence is changed to boolean precedence.
Parameters
----------
tok : tuple of int, str
ints correspond to the all caps constants in the tokenize module
Returns
-------
tuple of int, str
Either the input or token or the replacement values
"""
toknum, tokval = tok
if toknum == tokenize.OP:
if tokval == "&":
return tokenize.NAME, "and"
elif tokval == "|":
return tokenize.NAME, "or"
return toknum, tokval
return toknum, tokval
def _replace_locals(tok: tuple[int, str]) -> tuple[int, str]:
"""
Replace local variables with a syntactically valid name.
Parameters
----------
tok : tuple of int, str
ints correspond to the all caps constants in the tokenize module
Returns
-------
tuple of int, str
Either the input or token or the replacement values
Notes
-----
This is somewhat of a hack in that we rewrite a string such as ``'@a'`` as
``'__pd_eval_local_a'`` by telling the tokenizer that ``__pd_eval_local_``
is a ``tokenize.OP`` and to replace the ``'@'`` symbol with it.
"""
toknum, tokval = tok
if toknum == tokenize.OP and tokval == "@":
return tokenize.OP, LOCAL_TAG
return toknum, tokval
def _compose2(f, g):
"""
Compose 2 callables.
"""
return lambda *args, **kwargs: f(g(*args, **kwargs))
def _compose(*funcs):
"""
Compose 2 or more callables.
"""
assert len(funcs) > 1, "At least 2 callables must be passed to compose"
return reduce(_compose2, funcs)
def _preparse(
source: str,
f=_compose(
_replace_locals, _replace_booleans, _rewrite_assign, clean_backtick_quoted_toks
),
) -> str:
"""
Compose a collection of tokenization functions.
Parameters
----------
source : str
A Python source code string
f : callable
This takes a tuple of (toknum, tokval) as its argument and returns a
tuple with the same structure but possibly different elements. Defaults
to the composition of ``_rewrite_assign``, ``_replace_booleans``, and
``_replace_locals``.
Returns
-------
str
Valid Python source code
Notes
-----
The `f` parameter can be any callable that takes *and* returns input of the
form ``(toknum, tokval)``, where ``toknum`` is one of the constants from
the ``tokenize`` module and ``tokval`` is a string.
"""
assert callable(f), "f must be callable"
return tokenize.untokenize(f(x) for x in tokenize_string(source))
def _is_type(t):
"""
Factory for a type checking function of type ``t`` or tuple of types.
"""
return lambda x: isinstance(x.value, t)
_is_list = _is_type(list)
_is_str = _is_type(str)
# partition all AST nodes
_all_nodes = frozenset(
node
for node in (getattr(ast, name) for name in dir(ast))
if isinstance(node, type) and issubclass(node, ast.AST)
)
def _filter_nodes(superclass, all_nodes=_all_nodes):
"""
Filter out AST nodes that are subclasses of ``superclass``.
"""
node_names = (node.__name__ for node in all_nodes if issubclass(node, superclass))
return frozenset(node_names)
_all_node_names = frozenset(map(lambda x: x.__name__, _all_nodes))
_mod_nodes = _filter_nodes(ast.mod)
_stmt_nodes = _filter_nodes(ast.stmt)
_expr_nodes = _filter_nodes(ast.expr)
_expr_context_nodes = _filter_nodes(ast.expr_context)
_boolop_nodes = _filter_nodes(ast.boolop)
_operator_nodes = _filter_nodes(ast.operator)
_unary_op_nodes = _filter_nodes(ast.unaryop)
_cmp_op_nodes = _filter_nodes(ast.cmpop)
_comprehension_nodes = _filter_nodes(ast.comprehension)
_handler_nodes = _filter_nodes(ast.excepthandler)
_arguments_nodes = _filter_nodes(ast.arguments)
_keyword_nodes = _filter_nodes(ast.keyword)
_alias_nodes = _filter_nodes(ast.alias)
if not PY39:
_slice_nodes = _filter_nodes(ast.slice)
# nodes that we don't support directly but are needed for parsing
_hacked_nodes = frozenset(["Assign", "Module", "Expr"])
_unsupported_expr_nodes = frozenset(
[
"Yield",
"GeneratorExp",
"IfExp",
"DictComp",
"SetComp",
"Repr",
"Lambda",
"Set",
"AST",
"Is",
"IsNot",
]
)
# these nodes are low priority or won't ever be supported (e.g., AST)
_unsupported_nodes = (
_stmt_nodes
| _mod_nodes
| _handler_nodes
| _arguments_nodes
| _keyword_nodes
| _alias_nodes
| _expr_context_nodes
| _unsupported_expr_nodes
) - _hacked_nodes
# we're adding a different assignment in some cases to be equality comparison
# and we don't want `stmt` and friends in their so get only the class whose
# names are capitalized
_base_supported_nodes = (_all_node_names - _unsupported_nodes) | _hacked_nodes
intersection = _unsupported_nodes & _base_supported_nodes
_msg = f"cannot both support and not support {intersection}"
assert not intersection, _msg
def _node_not_implemented(node_name: str) -> Callable[..., None]:
"""
Return a function that raises a NotImplementedError with a passed node name.
"""
def f(self, *args, **kwargs):
raise NotImplementedError(f"'{node_name}' nodes are not implemented")
return f
# should be bound by BaseExprVisitor but that creates a circular dependency:
# _T is used in disallow, but disallow is used to define BaseExprVisitor
# https://github.com/microsoft/pyright/issues/2315
_T = TypeVar("_T")
def disallow(nodes: set[str]) -> Callable[[type[_T]], type[_T]]:
"""
Decorator to disallow certain nodes from parsing. Raises a
NotImplementedError instead.
Returns
-------
callable
"""
def disallowed(cls: type[_T]) -> type[_T]:
# error: "Type[_T]" has no attribute "unsupported_nodes"
cls.unsupported_nodes = () # type: ignore[attr-defined]
for node in nodes:
new_method = _node_not_implemented(node)
name = f"visit_{node}"
# error: "Type[_T]" has no attribute "unsupported_nodes"
cls.unsupported_nodes += (name,) # type: ignore[attr-defined]
setattr(cls, name, new_method)
return cls
return disallowed
def _op_maker(op_class, op_symbol):
"""
Return a function to create an op class with its symbol already passed.
Returns
-------
callable
"""
def f(self, node, *args, **kwargs):
"""
Return a partial function with an Op subclass with an operator already passed.
Returns
-------
callable
"""
return partial(op_class, op_symbol, *args, **kwargs)
return f
_op_classes = {"binary": BinOp, "unary": UnaryOp}
def add_ops(op_classes):
"""
Decorator to add default implementation of ops.
"""
def f(cls):
for op_attr_name, op_class in op_classes.items():
ops = getattr(cls, f"{op_attr_name}_ops")
ops_map = getattr(cls, f"{op_attr_name}_op_nodes_map")
for op in ops:
op_node = ops_map[op]
if op_node is not None:
made_op = _op_maker(op_class, op)
setattr(cls, f"visit_{op_node}", made_op)
return cls
return f
@disallow(_unsupported_nodes)
@add_ops(_op_classes)
class BaseExprVisitor(ast.NodeVisitor):
"""
Custom ast walker. Parsers of other engines should subclass this class
if necessary.
Parameters
----------
env : Scope
engine : str
parser : str
preparser : callable
"""
const_type: type[Term] = Constant
term_type = Term
binary_ops = CMP_OPS_SYMS + BOOL_OPS_SYMS + ARITH_OPS_SYMS
binary_op_nodes = (
"Gt",
"Lt",
"GtE",
"LtE",
"Eq",
"NotEq",
"In",
"NotIn",
"BitAnd",
"BitOr",
"And",
"Or",
"Add",
"Sub",
"Mult",
None,
"Pow",
"FloorDiv",
"Mod",
)
binary_op_nodes_map = dict(zip(binary_ops, binary_op_nodes))
unary_ops = UNARY_OPS_SYMS
unary_op_nodes = "UAdd", "USub", "Invert", "Not"
unary_op_nodes_map = dict(zip(unary_ops, unary_op_nodes))
rewrite_map = {
ast.Eq: ast.In,
ast.NotEq: ast.NotIn,
ast.In: ast.In,
ast.NotIn: ast.NotIn,
}
unsupported_nodes: tuple[str, ...]
def __init__(self, env, engine, parser, preparser=_preparse) -> None:
self.env = env
self.engine = engine
self.parser = parser
self.preparser = preparser
self.assigner = None
def visit(self, node, **kwargs):
if isinstance(node, str):
clean = self.preparser(node)
try:
node = ast.fix_missing_locations(ast.parse(clean))
except SyntaxError as e:
if any(iskeyword(x) for x in clean.split()):
e.msg = "Python keyword not valid identifier in numexpr query"
raise e
method = f"visit_{type(node).__name__}"
visitor = getattr(self, method)
return visitor(node, **kwargs)
def visit_Module(self, node, **kwargs):
if len(node.body) != 1:
raise SyntaxError("only a single expression is allowed")
expr = node.body[0]
return self.visit(expr, **kwargs)
def visit_Expr(self, node, **kwargs):
return self.visit(node.value, **kwargs)
def _rewrite_membership_op(self, node, left, right):
# the kind of the operator (is actually an instance)
op_instance = node.op
op_type = type(op_instance)
# must be two terms and the comparison operator must be ==/!=/in/not in
if is_term(left) and is_term(right) and op_type in self.rewrite_map:
left_list, right_list = map(_is_list, (left, right))
left_str, right_str = map(_is_str, (left, right))
# if there are any strings or lists in the expression
if left_list or right_list or left_str or right_str:
op_instance = self.rewrite_map[op_type]()
# pop the string variable out of locals and replace it with a list
# of one string, kind of a hack
if right_str:
name = self.env.add_tmp([right.value])
right = self.term_type(name, self.env)
if left_str:
name = self.env.add_tmp([left.value])
left = self.term_type(name, self.env)
op = self.visit(op_instance)
return op, op_instance, left, right
def _maybe_transform_eq_ne(self, node, left=None, right=None):
if left is None:
left = self.visit(node.left, side="left")
if right is None:
right = self.visit(node.right, side="right")
op, op_class, left, right = self._rewrite_membership_op(node, left, right)
return op, op_class, left, right
def _maybe_downcast_constants(self, left, right):
f32 = np.dtype(np.float32)
if (
left.is_scalar
and hasattr(left, "value")
and not right.is_scalar
and right.return_type == f32
):
# right is a float32 array, left is a scalar
name = self.env.add_tmp(np.float32(left.value))
left = self.term_type(name, self.env)
if (
right.is_scalar
and hasattr(right, "value")
and not left.is_scalar
and left.return_type == f32
):
# left is a float32 array, right is a scalar
name = self.env.add_tmp(np.float32(right.value))
right = self.term_type(name, self.env)
return left, right
def _maybe_eval(self, binop, eval_in_python):
# eval `in` and `not in` (for now) in "partial" python space
# things that can be evaluated in "eval" space will be turned into
# temporary variables. for example,
# [1,2] in a + 2 * b
# in that case a + 2 * b will be evaluated using numexpr, and the "in"
# call will be evaluated using isin (in python space)
return binop.evaluate(
self.env, self.engine, self.parser, self.term_type, eval_in_python
)
def _maybe_evaluate_binop(
self,
op,
op_class,
lhs,
rhs,
eval_in_python=("in", "not in"),
maybe_eval_in_python=("==", "!=", "<", ">", "<=", ">="),
):
res = op(lhs, rhs)
if res.has_invalid_return_type:
raise TypeError(
f"unsupported operand type(s) for {res.op}: "
f"'{lhs.type}' and '{rhs.type}'"
)
if self.engine != "pytables" and (
res.op in CMP_OPS_SYMS
and getattr(lhs, "is_datetime", False)
or getattr(rhs, "is_datetime", False)
):
# all date ops must be done in python bc numexpr doesn't work
# well with NaT
return self._maybe_eval(res, self.binary_ops)
if res.op in eval_in_python:
# "in"/"not in" ops are always evaluated in python
return self._maybe_eval(res, eval_in_python)
elif self.engine != "pytables":
if (
getattr(lhs, "return_type", None) == object
or getattr(rhs, "return_type", None) == object
):
# evaluate "==" and "!=" in python if either of our operands
# has an object return type
return self._maybe_eval(res, eval_in_python + maybe_eval_in_python)
return res
def visit_BinOp(self, node, **kwargs):
op, op_class, left, right = self._maybe_transform_eq_ne(node)
left, right = self._maybe_downcast_constants(left, right)
return self._maybe_evaluate_binop(op, op_class, left, right)
def visit_Div(self, node, **kwargs):
return lambda lhs, rhs: Div(lhs, rhs)
def visit_UnaryOp(self, node, **kwargs):
op = self.visit(node.op)
operand = self.visit(node.operand)
return op(operand)
def visit_Name(self, node, **kwargs):
return self.term_type(node.id, self.env, **kwargs)
def visit_NameConstant(self, node, **kwargs) -> Term:
return self.const_type(node.value, self.env)
def visit_Num(self, node, **kwargs) -> Term:
return self.const_type(node.n, self.env)
def visit_Constant(self, node, **kwargs) -> Term:
return self.const_type(node.n, self.env)
def visit_Str(self, node, **kwargs):
name = self.env.add_tmp(node.s)
return self.term_type(name, self.env)
def visit_List(self, node, **kwargs):
name = self.env.add_tmp([self.visit(e)(self.env) for e in node.elts])
return self.term_type(name, self.env)
visit_Tuple = visit_List
def visit_Index(self, node, **kwargs):
"""df.index[4]"""
return self.visit(node.value)
def visit_Subscript(self, node, **kwargs):
from pandas import eval as pd_eval
value = self.visit(node.value)
slobj = self.visit(node.slice)
result = pd_eval(
slobj, local_dict=self.env, engine=self.engine, parser=self.parser
)
try:
# a Term instance
v = value.value[result]
except AttributeError:
# an Op instance
lhs = pd_eval(
value, local_dict=self.env, engine=self.engine, parser=self.parser
)
v = lhs[result]
name = self.env.add_tmp(v)
return self.term_type(name, env=self.env)
def visit_Slice(self, node, **kwargs):
"""df.index[slice(4,6)]"""
lower = node.lower
if lower is not None:
lower = self.visit(lower).value
upper = node.upper
if upper is not None:
upper = self.visit(upper).value
step = node.step
if step is not None:
step = self.visit(step).value
return slice(lower, upper, step)
def visit_Assign(self, node, **kwargs):
"""
support a single assignment node, like
c = a + b
set the assigner at the top level, must be a Name node which
might or might not exist in the resolvers
"""
if len(node.targets) != 1:
raise SyntaxError("can only assign a single expression")
if not isinstance(node.targets[0], ast.Name):
raise SyntaxError("left hand side of an assignment must be a single name")
if self.env.target is None:
raise ValueError("cannot assign without a target object")
try:
assigner = self.visit(node.targets[0], **kwargs)
except UndefinedVariableError:
assigner = node.targets[0].id
self.assigner = getattr(assigner, "name", assigner)
if self.assigner is None:
raise SyntaxError(
"left hand side of an assignment must be a single resolvable name"
)
return self.visit(node.value, **kwargs)
def visit_Attribute(self, node, **kwargs):
attr = node.attr
value = node.value
ctx = node.ctx
if isinstance(ctx, ast.Load):
# resolve the value
resolved = self.visit(value).value
try:
v = getattr(resolved, attr)
name = self.env.add_tmp(v)
return self.term_type(name, self.env)
except AttributeError:
# something like datetime.datetime where scope is overridden
if isinstance(value, ast.Name) and value.id == attr:
return resolved
raise
raise ValueError(f"Invalid Attribute context {type(ctx).__name__}")
def visit_Call(self, node, side=None, **kwargs):
if isinstance(node.func, ast.Attribute) and node.func.attr != "__call__":
res = self.visit_Attribute(node.func)
elif not isinstance(node.func, ast.Name):
raise TypeError("Only named functions are supported")
else:
try:
res = self.visit(node.func)
except UndefinedVariableError:
# Check if this is a supported function name
try:
res = FuncNode(node.func.id)
except ValueError:
# Raise original error
raise
if res is None:
# error: "expr" has no attribute "id"
raise ValueError(
f"Invalid function call {node.func.id}" # type: ignore[attr-defined]
)
if hasattr(res, "value"):
res = res.value
if isinstance(res, FuncNode):
new_args = [self.visit(arg) for arg in node.args]
if node.keywords:
raise TypeError(
f'Function "{res.name}" does not support keyword arguments'
)
return res(*new_args)
else:
new_args = [self.visit(arg)(self.env) for arg in node.args]
for key in node.keywords:
if not isinstance(key, ast.keyword):
# error: "expr" has no attribute "id"
raise ValueError(
"keyword error in function call " # type: ignore[attr-defined]
f"'{node.func.id}'"
)
if key.arg:
kwargs[key.arg] = self.visit(key.value)(self.env)
name = self.env.add_tmp(res(*new_args, **kwargs))
return self.term_type(name=name, env=self.env)
def translate_In(self, op):
return op
def visit_Compare(self, node, **kwargs):
ops = node.ops
comps = node.comparators
# base case: we have something like a CMP b
if len(comps) == 1:
op = self.translate_In(ops[0])
binop = ast.BinOp(op=op, left=node.left, right=comps[0])
return self.visit(binop)
# recursive case: we have a chained comparison, a CMP b CMP c, etc.
left = node.left
values = []
for op, comp in zip(ops, comps):
new_node = self.visit(
ast.Compare(comparators=[comp], left=left, ops=[self.translate_In(op)])
)
left = comp
values.append(new_node)
return self.visit(ast.BoolOp(op=ast.And(), values=values))
def _try_visit_binop(self, bop):
if isinstance(bop, (Op, Term)):
return bop
return self.visit(bop)
def visit_BoolOp(self, node, **kwargs):
def visitor(x, y):
lhs = self._try_visit_binop(x)
rhs = self._try_visit_binop(y)
op, op_class, lhs, rhs = self._maybe_transform_eq_ne(node, lhs, rhs)
return self._maybe_evaluate_binop(op, node.op, lhs, rhs)
operands = node.values
return reduce(visitor, operands)
_python_not_supported = frozenset(["Dict", "BoolOp", "In", "NotIn"])
_numexpr_supported_calls = frozenset(REDUCTIONS + MATHOPS)
@disallow(
(_unsupported_nodes | _python_not_supported)
- (_boolop_nodes | frozenset(["BoolOp", "Attribute", "In", "NotIn", "Tuple"]))
)
class PandasExprVisitor(BaseExprVisitor):
def __init__(
self,
env,
engine,
parser,
preparser=partial(
_preparse,
f=_compose(_replace_locals, _replace_booleans, clean_backtick_quoted_toks),
),
) -> None:
super().__init__(env, engine, parser, preparser)
@disallow(_unsupported_nodes | _python_not_supported | frozenset(["Not"]))
class PythonExprVisitor(BaseExprVisitor):
def __init__(
self, env, engine, parser, preparser=lambda source, f=None: source
) -> None:
super().__init__(env, engine, parser, preparser=preparser)
class Expr:
"""
Object encapsulating an expression.
Parameters
----------
expr : str
engine : str, optional, default 'numexpr'
parser : str, optional, default 'pandas'
env : Scope, optional, default None
level : int, optional, default 2
"""
env: Scope
engine: str
parser: str
def __init__(
self,
expr,
engine: str = "numexpr",
parser: str = "pandas",
env: Scope | None = None,
level: int = 0,
) -> None:
self.expr = expr
self.env = env or Scope(level=level + 1)
self.engine = engine
self.parser = parser
self._visitor = PARSERS[parser](self.env, self.engine, self.parser)
self.terms = self.parse()
@property
def assigner(self):
return getattr(self._visitor, "assigner", None)
def __call__(self):
return self.terms(self.env)
def __repr__(self) -> str:
return printing.pprint_thing(self.terms)
def __len__(self) -> int:
return len(self.expr)
def parse(self):
"""
Parse an expression.
"""
return self._visitor.visit(self.expr)
@property
def names(self):
"""
Get the names in an expression.
"""
if is_term(self.terms):
return frozenset([self.terms.name])
return frozenset(term.name for term in com.flatten(self.terms))
PARSERS = {"python": PythonExprVisitor, "pandas": PandasExprVisitor}