cpython/Lib/symtable.py at main · python/cpython · GitHub

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"""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,

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, *, module=None):

""" Return the toplevel *SymbolTable* for the source code.

*code* can be a string, a bytes object, or an AST object.

*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, module=module)

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"

INLINED_COMPREHENSION = "inlined comprehension"

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

if self._table.type == _symtable.TYPE_INLINED_COMPREHENSION:

return SymbolTableType.INLINED_COMPREHENSION

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")

inlined = (self._table.type == _symtable.TYPE_INLINED_COMPREHENSION)

sym = self._symbols[name] = Symbol(name, flags, namespaces,

module_scope=module_scope,

inlined_comprehension=inlined)

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

__cells = 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

def get_cells(self):

"""Return a tuple of cell variables in the function.

"""

if self.__cells is None:

is_cell = lambda x: _get_scope(x) == CELL

self.__cells = self.__idents_matching(is_cell)

return self.__cells

class Class(SymbolTable):

pass

class Symbol:

def __init__(self, name, flags, namespaces=None, *, module_scope=False,

inlined_comprehension=False):

self.__name = name

self.__flags = flags

self.__scope = _get_scope(flags)

self.__namespaces = namespaces or ()

self.__module_scope = module_scope

self.__inlined_comprehension = inlined_comprehension

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_cell(self):

"""Return *True* if the symbol is a cell variable."""

return bool(self.__scope == CELL)

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 self.is_cell() and self.__inlined_comprehension

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 = frozendict({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:])

cpython/Lib/symtable.py at main · python/cpython · GitHub

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