"""Interface to the compiler's internal symbol tables"""
import _symtable
from _symtable import (
USE,
DEF_GLOBAL, # noqa: F401
DEF_NONLOCAL, DEF_LOCAL,
DEF_PARAM, DEF_TYPE_PARAM, DEF_FREE_CLASS,
DEF_IMPORT, DEF_BOUND, DEF_ANNOT,
DEF_COMP_ITER, DEF_COMP_CELL,
SCOPE_OFF, SCOPE_MASK,
FREE, LOCAL, GLOBAL_IMPLICIT, GLOBAL_EXPLICIT, CELL
)
import weakref
from enum import StrEnum
__all__ = ["symtable", "SymbolTableType", "SymbolTable", "Class", "Function", "Symbol"]
def symtable(code, filename, compile_type):
""" Return the toplevel *SymbolTable* for the source code.
*filename* is the name of the file with the code
and *compile_type* is the *compile()* mode argument.
"""
top = _symtable.symtable(code, filename, compile_type)
return _newSymbolTable(top, filename)
class SymbolTableFactory:
def __init__(self):
self.__memo = weakref.WeakValueDictionary()
def new(self, table, filename):
if table.type == _symtable.TYPE_FUNCTION:
return Function(table, filename)
if table.type == _symtable.TYPE_CLASS:
return Class(table, filename)
return SymbolTable(table, filename)
def __call__(self, table, filename):
key = table, filename
obj = self.__memo.get(key, None)
if obj is None:
obj = self.__memo[key] = self.new(table, filename)
return obj
_newSymbolTable = SymbolTableFactory()
class SymbolTableType(StrEnum):
MODULE = "module"
FUNCTION = "function"
CLASS = "class"
ANNOTATION = "annotation"
TYPE_ALIAS = "type alias"
TYPE_PARAMETERS = "type parameters"
TYPE_VARIABLE = "type variable"
class SymbolTable:
def __init__(self, raw_table, filename):
self._table = raw_table
self._filename = filename
self._symbols = {}
def __repr__(self):
if self.__class__ == SymbolTable:
kind = ""
else:
kind = "%s " % self.__class__.__name__
if self._table.name == "top":
return "<{0}SymbolTable for module {1}>".format(kind, self._filename)
else:
return "<{0}SymbolTable for {1} in {2}>".format(kind,
self._table.name,
self._filename)
def get_type(self):
"""Return the type of the symbol table.
The value returned is one of the values in
the ``SymbolTableType`` enumeration.
"""
if self._table.type == _symtable.TYPE_MODULE:
return SymbolTableType.MODULE
if self._table.type == _symtable.TYPE_FUNCTION:
return SymbolTableType.FUNCTION
if self._table.type == _symtable.TYPE_CLASS:
return SymbolTableType.CLASS
if self._table.type == _symtable.TYPE_ANNOTATION:
return SymbolTableType.ANNOTATION
if self._table.type == _symtable.TYPE_TYPE_ALIAS:
return SymbolTableType.TYPE_ALIAS
if self._table.type == _symtable.TYPE_TYPE_PARAMETERS:
return SymbolTableType.TYPE_PARAMETERS
if self._table.type == _symtable.TYPE_TYPE_VARIABLE:
return SymbolTableType.TYPE_VARIABLE
assert False, f"unexpected type: {self._table.type}"
def get_id(self):
"""Return an identifier for the table.
"""
return self._table.id
def get_name(self):
"""Return the table's name.
This corresponds to the name of the class, function
or 'top' if the table is for a class, function or
global respectively.
"""
return self._table.name
def get_lineno(self):
"""Return the number of the first line in the
block for the table.
"""
return self._table.lineno
def is_optimized(self):
"""Return *True* if the locals in the table
are optimizable.
"""
return bool(self._table.type == _symtable.TYPE_FUNCTION)
def is_nested(self):
"""Return *True* if the block is a nested class
or function."""
return bool(self._table.nested)
def has_children(self):
"""Return *True* if the block has nested namespaces.
"""
return bool(self._table.children)
def get_identifiers(self):
"""Return a view object containing the names of symbols in the table.
"""
return self._table.symbols.keys()
def lookup(self, name):
"""Lookup a *name* in the table.
Returns a *Symbol* instance.
"""
sym = self._symbols.get(name)
if sym is None:
flags = self._table.symbols[name]
namespaces = self.__check_children(name)
module_scope = (self._table.name == "top")
sym = self._symbols[name] = Symbol(name, flags, namespaces,
module_scope=module_scope)
return sym
def get_symbols(self):
"""Return a list of *Symbol* instances for
names in the table.
"""
return [self.lookup(ident) for ident in self.get_identifiers()]
def __check_children(self, name):
return [_newSymbolTable(st, self._filename)
for st in self._table.children
if st.name == name]
def get_children(self):
"""Return a list of the nested symbol tables.
"""
return [_newSymbolTable(st, self._filename)
for st in self._table.children]
def _get_scope(flags): # like _PyST_GetScope()
return (flags >> SCOPE_OFF) & SCOPE_MASK
class Function(SymbolTable):
# Default values for instance variables
__params = None
__locals = None
__frees = None
__globals = None
__nonlocals = None
def __idents_matching(self, test_func):
return tuple(ident for ident in self.get_identifiers()
if test_func(self._table.symbols[ident]))
def get_parameters(self):
"""Return a tuple of parameters to the function.
"""
if self.__params is None:
self.__params = self.__idents_matching(lambda x:x & DEF_PARAM)
return self.__params
def get_locals(self):
"""Return a tuple of locals in the function.
"""
if self.__locals is None:
locs = (LOCAL, CELL)
test = lambda x: _get_scope(x) in locs
self.__locals = self.__idents_matching(test)
return self.__locals
def get_globals(self):
"""Return a tuple of globals in the function.
"""
if self.__globals is None:
glob = (GLOBAL_IMPLICIT, GLOBAL_EXPLICIT)
test = lambda x: _get_scope(x) in glob
self.__globals = self.__idents_matching(test)
return self.__globals
def get_nonlocals(self):
"""Return a tuple of nonlocals in the function.
"""
if self.__nonlocals is None:
self.__nonlocals = self.__idents_matching(lambda x:x & DEF_NONLOCAL)
return self.__nonlocals
def get_frees(self):
"""Return a tuple of free variables in the function.
"""
if self.__frees is None:
is_free = lambda x: _get_scope(x) == FREE
self.__frees = self.__idents_matching(is_free)
return self.__frees
class Class(SymbolTable):
__methods = None
def get_methods(self):
"""Return a tuple of methods declared in the class.
"""
import warnings
typename = f'{self.__class__.__module__}.{self.__class__.__name__}'
warnings.warn(f'{typename}.get_methods() is deprecated '
f'and will be removed in Python 3.16.',
DeprecationWarning, stacklevel=2)
if self.__methods is None:
d = {}
def is_local_symbol(ident):
flags = self._table.symbols.get(ident, 0)
return ((flags >> SCOPE_OFF) & SCOPE_MASK) == LOCAL
for st in self._table.children:
# pick the function-like symbols that are local identifiers
if is_local_symbol(st.name):
match st.type:
case _symtable.TYPE_FUNCTION:
# generators are of type TYPE_FUNCTION with a ".0"
# parameter as a first parameter (which makes them
# distinguishable from a function named 'genexpr')
if st.name == 'genexpr' and '.0' in st.varnames:
continue
d[st.name] = 1
case _symtable.TYPE_TYPE_PARAMETERS:
# Get the function-def block in the annotation
# scope 'st' with the same identifier, if any.
scope_name = st.name
for c in st.children:
if c.name == scope_name and c.type == _symtable.TYPE_FUNCTION:
# A generic generator of type TYPE_FUNCTION
# cannot be a direct child of 'st' (but it
# can be a descendant), e.g.:
#
# class A:
# type genexpr[genexpr] = (x for x in [])
assert scope_name != 'genexpr' or '.0' not in c.varnames
d[scope_name] = 1
break
self.__methods = tuple(d)
return self.__methods
class Symbol:
def __init__(self, name, flags, namespaces=None, *, module_scope=False):
self.__name = name
self.__flags = flags
self.__scope = _get_scope(flags)
self.__namespaces = namespaces or ()
self.__module_scope = module_scope
def __repr__(self):
flags_str = '|'.join(self._flags_str())
return f'<symbol {self.__name!r}: {self._scope_str()}, {flags_str}>'
def _scope_str(self):
return _scopes_value_to_name.get(self.__scope) or str(self.__scope)
def _flags_str(self):
for flagname, flagvalue in _flags:
if self.__flags & flagvalue == flagvalue:
yield flagname
def get_name(self):
"""Return a name of a symbol.
"""
return self.__name
def is_referenced(self):
"""Return *True* if the symbol is used in
its block.
"""
return bool(self.__flags & USE)
def is_parameter(self):
"""Return *True* if the symbol is a parameter.
"""
return bool(self.__flags & DEF_PARAM)
def is_type_parameter(self):
"""Return *True* if the symbol is a type parameter.
"""
return bool(self.__flags & DEF_TYPE_PARAM)
def is_global(self):
"""Return *True* if the symbol is global.
"""
return bool(self.__scope in (GLOBAL_IMPLICIT, GLOBAL_EXPLICIT)
or (self.__module_scope and self.__flags & DEF_BOUND))
def is_nonlocal(self):
"""Return *True* if the symbol is nonlocal."""
return bool(self.__flags & DEF_NONLOCAL)
def is_declared_global(self):
"""Return *True* if the symbol is declared global
with a global statement."""
return bool(self.__scope == GLOBAL_EXPLICIT)
def is_local(self):
"""Return *True* if the symbol is local.
"""
return bool(self.__scope in (LOCAL, CELL)
or (self.__module_scope and self.__flags & DEF_BOUND))
def is_annotated(self):
"""Return *True* if the symbol is annotated.
"""
return bool(self.__flags & DEF_ANNOT)
def is_free(self):
"""Return *True* if a referenced symbol is
not assigned to.
"""
return bool(self.__scope == FREE)
def is_free_class(self):
"""Return *True* if a class-scoped symbol is free from
the perspective of a method."""
return bool(self.__flags & DEF_FREE_CLASS)
def is_imported(self):
"""Return *True* if the symbol is created from
an import statement.
"""
return bool(self.__flags & DEF_IMPORT)
def is_assigned(self):
"""Return *True* if a symbol is assigned to."""
return bool(self.__flags & DEF_LOCAL)
def is_comp_iter(self):
"""Return *True* if the symbol is a comprehension iteration variable.
"""
return bool(self.__flags & DEF_COMP_ITER)
def is_comp_cell(self):
"""Return *True* if the symbol is a cell in an inlined comprehension.
"""
return bool(self.__flags & DEF_COMP_CELL)
def is_namespace(self):
"""Returns *True* if name binding introduces new namespace.
If the name is used as the target of a function or class
statement, this will be true.
Note that a single name can be bound to multiple objects. If
is_namespace() is true, the name may also be bound to other
objects, like an int or list, that does not introduce a new
namespace.
"""
return bool(self.__namespaces)
def get_namespaces(self):
"""Return a list of namespaces bound to this name"""
return self.__namespaces
def get_namespace(self):
"""Return the single namespace bound to this name.
Raises ValueError if the name is bound to multiple namespaces
or no namespace.
"""
if len(self.__namespaces) == 0:
raise ValueError("name is not bound to any namespaces")
elif len(self.__namespaces) > 1:
raise ValueError("name is bound to multiple namespaces")
else:
return self.__namespaces[0]
_flags = [('USE', USE)]
_flags.extend(kv for kv in globals().items() if kv[0].startswith('DEF_'))
_scopes_names = ('FREE', 'LOCAL', 'GLOBAL_IMPLICIT', 'GLOBAL_EXPLICIT', 'CELL')
_scopes_value_to_name = {globals()[n]: n for n in _scopes_names}
def main(args):
import sys
def print_symbols(table, level=0):
indent = ' ' * level
nested = "nested " if table.is_nested() else ""
if table.get_type() == 'module':
what = f'from file {table._filename!r}'
else:
what = f'{table.get_name()!r}'
print(f'{indent}symbol table for {nested}{table.get_type()} {what}:')
for ident in table.get_identifiers():
symbol = table.lookup(ident)
flags = ', '.join(symbol._flags_str()).lower()
print(f' {indent}{symbol._scope_str().lower()} symbol {symbol.get_name()!r}: {flags}')
print()
for table2 in table.get_children():
print_symbols(table2, level + 1)
for filename in args or ['-']:
if filename == '-':
src = sys.stdin.read()
filename = '<stdin>'
else:
with open(filename, 'rb') as f:
src = f.read()
mod = symtable(src, filename, 'exec')
print_symbols(mod)
if __name__ == "__main__":
import sys
main(sys.argv[1:])
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