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Merge pull request #121 from newville/with_namespace
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add optional (non-default) nested symbol table
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@newville
newville authored Jul 16, 2023
2 parents 5eaad18 + f511b1a commit 725ffed
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Showing 9 changed files with 2,897 additions and 1,207 deletions.
71 changes: 41 additions & 30 deletions asteval/asteval.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,9 +16,10 @@
compiled into ast node and then evaluated later, using the current values
in the symbol table.
The result is a restricted, simplified version of Python meant for
numerical calculations that is somewhat safer than 'eval' because many
unsafe operations (such as 'import' and 'eval') are simply not allowed.
The result is a restricted, simplified version of Python meant for numerical
calculations that is somewhat safer than 'eval' because many unsafe operations
(such as 'eval') are simply not allowed, and others (such as 'import') are
disabled by default, but can be explicitly enabled.
Many parts of Python syntax are supported, including:
for loops, while loops, if-then-elif-else conditionals, with,
Expand All @@ -34,7 +35,7 @@
In addition, while many builtin functions are supported, several builtin
functions that are considered unsafe are missing ('eval', 'exec', and
'getattr' for example)
'getattr' for example) are missing.
"""
import ast
import sys
Expand All @@ -43,7 +44,7 @@
import time
from sys import exc_info, stderr, stdout

from .astutils import (HAS_NUMPY, UNSAFE_ATTRS, ExceptionHolder, ReturnedNone,
from .astutils import (HAS_NUMPY, UNSAFE_ATTRS, ExceptionHolder, ReturnedNone, Empty,
make_symbol_table, numpy, op2func, valid_symbol_name,
Procedure)

Expand All @@ -61,11 +62,11 @@
MINIMAL_CONFIG = {'import': False, 'importfrom': False}
DEFAULT_CONFIG = {'import': False, 'importfrom': False}

for node in ('assert', 'augassign', 'delete', 'if', 'ifexp', 'for',
for _tnode in ('assert', 'augassign', 'delete', 'if', 'ifexp', 'for',
'formattedvalue', 'functiondef', 'print', 'raise', 'listcomp',
'dictcomp', 'setcomp', 'try', 'while', 'with'):
MINIMAL_CONFIG[node] = False
DEFAULT_CONFIG[node] = True
MINIMAL_CONFIG[_tnode] = False
DEFAULT_CONFIG[_tnode] = True

class Interpreter:
"""create an asteval Interpreter: a restricted, simplified interpreter
Expand All @@ -74,8 +75,10 @@ class Interpreter:
Parameters
----------
symtable : dict or `None`
dictionary to use as symbol table (if `None`, one will be created).
usersyms : dict or `None`
dictionary or SymbolTable to use as symbol table (if `None`, one will be created).
nested_symtable : bool, optional
whether to use a new-style nested symbol table instead of a plain dict [False]
user_symbols : dict or `None`
dictionary of user-defined symbols to add to symbol table.
writer : file-like or `None`
callable file-like object where standard output will be sent.
Expand All @@ -102,14 +105,21 @@ class Interpreter:
'assert', 'delete', 'raise', 'print')
2. by default 'import' and 'importfrom' are disabled, though they can be enabled.
"""
def __init__(self, symtable=None, usersyms=None, writer=None,
err_writer=None, use_numpy=True, max_statement_length=50000,
minimal=False, readonly_symbols=None, builtins_readonly=False,
config=None, **kws):
def __init__(self, symtable=None, nested_symtable=False,
user_symbols=None, writer=None, err_writer=None,
use_numpy=True, max_statement_length=50000,
minimal=False, readonly_symbols=None,
builtins_readonly=False, config=None, **kws):

self.config = copy.copy(MINIMAL_CONFIG if minimal else DEFAULT_CONFIG)
if config is not None:
self.config.update(config)
self.config['nested_symtable'] = nested_symtable

if user_symbols is None:
user_symbols = {}
if 'usersyms' in kws:
user_symbols = kws.pop('usersyms') # back compat, changed July, 2023, v 0.9.4

if len(kws) > 0:
for key, val in kws.items():
Expand All @@ -126,10 +136,10 @@ def __init__(self, symtable=None, usersyms=None, writer=None,
self.err_writer = err_writer or stderr
self.max_statement_length = max(1, min(1.e8, max_statement_length))

self.use_numpy = HAS_NUMPY and use_numpy
if symtable is None:
if usersyms is None:
usersyms = {}
symtable = make_symbol_table(use_numpy=use_numpy, **usersyms)
symtable = make_symbol_table(nested=nested_symtable,
use_numpy=self.use_numpy, **user_symbols)

symtable['print'] = self._printer
self.symtable = symtable
Expand All @@ -141,7 +151,6 @@ def __init__(self, symtable=None, usersyms=None, writer=None,
self._calldepth = 0
self.lineno = 0
self.start_time = time.time()
self.use_numpy = HAS_NUMPY and use_numpy

self.node_handlers = {}
for node in ALL_NODES:
Expand Down Expand Up @@ -333,7 +342,7 @@ def eval(self, expr, lineno=0, show_errors=True, raise_errors=False):
raise exc(errmsg)
if show_errors:
print(errmsg, file=self.err_writer)

return None

@staticmethod
def dump(node, **kw):
Expand Down Expand Up @@ -505,15 +514,19 @@ def on_formattedvalue(self, node): # ('value', 'conversion', 'format_spec')
fmt = f'{{0:{self.run(node.format_spec)}}}'
return fmt.format(val)

def _getsym(self, node):
val = self.symtable.get(node.id, ReturnedNone)
if isinstance(val, Empty):
msg = f"name '{node.id}' is not defined"
self.raise_exception(node, exc=NameError, msg=msg)
return val

def on_name(self, node): # ('id', 'ctx')
"""Name node."""
ctx = node.ctx.__class__
if ctx in (ast.Param, ast.Del):
return str(node.id)
if node.id in self.symtable:
return self.symtable[node.id]
msg = f"name '{node.id}' is not defined"
self.raise_exception(node, exc=NameError, msg=msg)
return self._getsym(node)

def on_nameconstant(self, node):
"""True, False, or None deprecated in 3.8"""
Expand Down Expand Up @@ -575,6 +588,7 @@ def on_attribute(self, node): # ('value', 'attr', 'ctx')
# AttributeError or accessed unsafe attribute
msg = f"no attribute '{node.attr}' for {self.run(node.value)}"
self.raise_exception(node, exc=AttributeError, msg=msg)
return None

def on_assign(self, node): # ('targets', 'value')
"""Simple assignment."""
Expand Down Expand Up @@ -608,6 +622,7 @@ def on_subscript(self, node): # ('value', 'slice', 'ctx')
return val[nslice]
msg = "subscript with unknown context"
self.raise_exception(node, msg=msg)
return None

def on_delete(self, node): # ('targets',)
"""Delete statement."""
Expand Down Expand Up @@ -760,14 +775,14 @@ def comprehension_data(self, node): # ('elt', 'generators')
self.raise_exception(tnode.target, exc=NameError, msg=errmsg)
mylocals[tnode.target.id] = []
if tnode.target.id in self.symtable:
saved_syms[tnode.target.id] = copy.deepcopy(self.symtable[tnode.target.id])
saved_syms[tnode.target.id] = copy.deepcopy(self._getsym(tnode.target))

elif tnode.target.__class__ == ast.Tuple:
target = []
for tval in tnode.target.elts:
mylocals[tval.id] = []
if tval.id in self.symtable:
saved_syms[tval.id] = copy.deepcopy(self.symtable[tval.id])
saved_syms[tval.id] = copy.deepcopy(self._getsym(tval))

for tnode in node.generators:
if tnode.__class__ == ast.comprehension:
Expand Down Expand Up @@ -888,17 +903,15 @@ def on_raise(self, node): # ('type', 'inst', 'tback')
msg = ' '.join(out.args)
msg2 = self.run(msgnode)
if msg2 not in (None, 'None'):
msg = "%s: %s" % (msg, msg2)
msg = f"{msg:s}: {msg2:s}"
self.raise_exception(None, exc=out.__class__, msg=msg, expr='')

def on_call(self, node):
"""Function execution."""
# ('func', 'args', 'keywords'. Py<3.5 has 'starargs' and 'kwargs' too)
func = self.run(node.func)
if not hasattr(func, '__call__') and not isinstance(func, type):
msg = f"'{func}' is not callable!!"
self.raise_exception(node, exc=TypeError, msg=msg)

args = [self.run(targ) for targ in node.args]
starargs = getattr(node, 'starargs', None)
if starargs is not None:
Expand Down Expand Up @@ -969,14 +982,12 @@ def on_functiondef(self, node):
# deprecation warning: will become
# doc = nb0.value
doc = nb0.value.s

varkws = node.args.kwarg
vararg = node.args.vararg
if isinstance(vararg, ast.arg):
vararg = vararg.arg
if isinstance(varkws, ast.arg):
varkws = varkws.arg

self.symtable[node.name] = Procedure(node.name, self, doc=doc,
lineno=self.lineno,
body=node.body,
Expand Down
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