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GeezerVison is showing github.com — cpython/Lib/ast.py at 3.15 · python/cpython Expand file tree/ Copy pathast.pyMore file actions 718 lines (620 loc) · 26 KB / Copy pathast.pyFile metadata and controls718 lines (620 loc) · 26 KB 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 """ The `ast` module helps Python applications to process trees of the Python abstract syntax grammar. The abstract syntax itself might change with each Python release; this module helps to find out programmatically what the current grammar looks like and allows modifications of it. An abstract syntax tree can be generated by passing `ast.PyCF_ONLY_AST` as a flag to the `compile()` builtin function or by using the `parse()` function from this module. The result will be a tree of objects whose classes all inherit from `ast.AST`. A modified abstract syntax tree can be compiled into a Python code object using the built-in `compile()` function. Additionally various helper functions are provided that make working with the trees simpler. The main intention of the helper functions and this module in general is to provide an easy to use interface for libraries that work tightly with the python syntax (template engines for example). :copyright: Copyright 2008 by Armin Ronacher. :license: Python License. """ from _ast import * def parse(source, filename='<unknown>', mode='exec', *, type_comments=False, feature_version=None, optimize=-1, module=None): """ Parse the source into an AST node. Equivalent to compile(source, filename, mode, PyCF_ONLY_AST). Pass type_comments=True to get back type comments where the syntax allows. """ flags = PyCF_ONLY_AST if optimize > 0: flags |= PyCF_OPTIMIZED_AST if type_comments: flags |= PyCF_TYPE_COMMENTS if feature_version is None: feature_version = -1 elif isinstance(feature_version, tuple): major, minor = feature_version # Should be a 2-tuple. if major != 3: raise ValueError(f"Unsupported major version: {major}") feature_version = minor # Else it should be an int giving the minor version for 3.x. return compile(source, filename, mode, flags, _feature_version=feature_version, optimize=optimize, module=module) def literal_eval(node_or_string): """ Evaluate an expression node or a string containing only a Python expression. The string or node provided may only consist of the following Python literal structures: strings, bytes, numbers, tuples, lists, dicts, sets, booleans, and None. Caution: A complex expression can overflow the C stack and cause a crash. """ if isinstance(node_or_string, str): node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval').body elif isinstance(node_or_string, Expression): node_or_string = node_or_string.body return _convert_literal(node_or_string) def _convert_literal(node): """ Used by `literal_eval` to convert an AST node into a value. """ if isinstance(node, Constant): return node.value if isinstance(node, Dict) and len(node.keys) == len(node.values): return dict(zip( map(_convert_literal, node.keys), map(_convert_literal, node.values), )) if isinstance(node, Tuple): return tuple(map(_convert_literal, node.elts)) if isinstance(node, List): return list(map(_convert_literal, node.elts)) if isinstance(node, Set): return set(map(_convert_literal, node.elts)) if ( isinstance(node, Call) and isinstance(node.func, Name) and node.func.id == 'set' and node.args == node.keywords == [] ): return set() if ( isinstance(node, UnaryOp) and isinstance(node.op, (UAdd, USub)) and isinstance(node.operand, Constant) and type(operand := node.operand.value) in (int, float, complex) ): if isinstance(node.op, UAdd): return + operand else: return - operand if ( isinstance(node, BinOp) and isinstance(node.op, (Add, Sub)) and isinstance(node.left, (Constant, UnaryOp)) and isinstance(node.right, Constant) and type(left := _convert_literal(node.left)) in (int, float) and type(right := _convert_literal(node.right)) is complex ): if isinstance(node.op, Add): return left + right else: return left - right msg = "malformed node or string" if lno := getattr(node, 'lineno', None): msg += f' on line {lno}' raise ValueError(msg + f': {node!r}') def dump( node, annotate_fields=True, include_attributes=False, *, color=False, indent=None, show_empty=False, ): """ Return a formatted dump of the tree in node. This is mainly useful for debugging purposes. If annotate_fields is true (by default), the returned string will show the names and the values for fields. If annotate_fields is false, the result string will be more compact by omitting unambiguous field names. Attributes such as line numbers and column offsets are not dumped by default. If this is wanted, include_attributes can be set to true. If color is true, the returned string is syntax highlighted using ANSI escape sequences. If color is false (the default), colored output is always disabled. If indent is a non-negative integer or string, then the tree will be pretty-printed with that indent level. If indent is None (the default), the tree is dumped on a single line. If show_empty is False, then empty lists and fields that are None will be omitted from the output for better readability. """ from _colorize import get_theme t = get_theme(force_color=color, force_no_color=not color).ast def _format(node, level=0): if indent is not None: level += 1 prefix = '\n' + indent * level sep = ',\n' + indent * level else: prefix = '' sep = ', ' if isinstance(node, AST): cls = type(node) args = [] args_buffer = [] allsimple = True keywords = annotate_fields for name in node._fields: try: value = getattr(node, name) except AttributeError: keywords = True continue if value is None and getattr(cls, name, ...) is None: keywords = True continue if not show_empty: if value == []: field_type = cls._field_types.get(name, object) if getattr(field_type, '__origin__', ...) is list: if not keywords: args_buffer.append(repr(value)) continue elif isinstance(value, Load): field_type = cls._field_types.get(name, object) if field_type is expr_context: if not keywords: args_buffer.append( f'{t.node}{type(value).__name__}' f'{t.reset}()') continue if not keywords: args.extend(args_buffer) args_buffer = [] value, simple = _format(value, level) allsimple = allsimple and simple if keywords: args.append(f'{t.field}{name}{t.reset}={value}') else: args.append(value) if include_attributes and node._attributes: for name in node._attributes: try: value = getattr(node, name) except AttributeError: continue if value is None and getattr(cls, name, ...) is None: continue value, simple = _format(value, level) allsimple = allsimple and simple args.append(f'{t.attribute}{name}{t.reset}={value}') cls_name = f'{t.node}{cls.__name__}{t.reset}' if allsimple and len(args) <= 3: return f'{cls_name}({", ".join(args)})', not args return f'{cls_name}({prefix}{sep.join(args)})', False elif isinstance(node, list): if not node: return '[]', True return '[%s%s]' % (prefix, sep.join(_format(x, level)[0] for x in node)), False if isinstance(node, bool) or node is None or node is Ellipsis: return f'{t.keyword}{node!r}{t.reset}', True if isinstance(node, (int, float, complex)): return f'{t.number}{node!r}{t.reset}', True if isinstance(node, (str, bytes)): return f'{t.string}{node!r}{t.reset}', True return repr(node), True if not isinstance(node, AST): raise TypeError('expected AST, got %r' % node.__class__.__name__) if indent is not None and not isinstance(indent, str): indent = ' ' * indent return _format(node)[0] def copy_location(new_node, old_node): """ Copy source location (`lineno`, `col_offset`, `end_lineno`, and `end_col_offset` attributes) from *old_node* to *new_node* if possible, and return *new_node*. """ for attr in 'lineno', 'col_offset', 'end_lineno', 'end_col_offset': if attr in old_node._attributes and attr in new_node._attributes: value = getattr(old_node, attr, None) # end_lineno and end_col_offset are optional attributes, and they # should be copied whether the value is None or not. if value is not None or ( hasattr(old_node, attr) and attr.startswith("end_") ): setattr(new_node, attr, value) return new_node def fix_missing_locations(node): """ When you compile a node tree with compile(), the compiler expects lineno and col_offset attributes for every node that supports them. This is rather tedious to fill in for generated nodes, so this helper adds these attributes recursively where not already set, by setting them to the values of the parent node. It works recursively starting at *node*. """ def _fix(node, lineno, col_offset, end_lineno, end_col_offset): if 'lineno' in node._attributes: if not hasattr(node, 'lineno'): node.lineno = lineno else: lineno = node.lineno if 'end_lineno' in node._attributes: if getattr(node, 'end_lineno', None) is None: node.end_lineno = end_lineno else: end_lineno = node.end_lineno if 'col_offset' in node._attributes: if not hasattr(node, 'col_offset'): node.col_offset = col_offset else: col_offset = node.col_offset if 'end_col_offset' in node._attributes: if getattr(node, 'end_col_offset', None) is None: node.end_col_offset = end_col_offset else: end_col_offset = node.end_col_offset for child in iter_child_nodes(node): _fix(child, lineno, col_offset, end_lineno, end_col_offset) _fix(node, 1, 0, 1, 0) return node def increment_lineno(node, n=1): """ Increment the line number and end line number of each node in the tree starting at *node* by *n*. This is useful to "move code" to a different location in a file. """ for child in walk(node): # TypeIgnore is a special case where lineno is not an attribute # but rather a field of the node itself. if isinstance(child, TypeIgnore): child.lineno = getattr(child, 'lineno', 0) + n continue if 'lineno' in child._attributes: child.lineno = getattr(child, 'lineno', 0) + n if ( "end_lineno" in child._attributes and (end_lineno := getattr(child, "end_lineno", 0)) is not None ): child.end_lineno = end_lineno + n return node def iter_fields(node): """ Yield a tuple of ``(fieldname, value)`` for each field in ``node._fields`` that is present on *node*. """ for field in node._fields: try: yield field, getattr(node, field) except AttributeError: pass def iter_child_nodes(node): """ Yield all direct child nodes of *node*, that is, all fields that are nodes and all items of fields that are lists of nodes. """ for name, field in iter_fields(node): if isinstance(field, AST): yield field elif isinstance(field, list): for item in field: if isinstance(item, AST): yield item def get_docstring(node, clean=True): """ Return the docstring for the given node or None if no docstring can be found. If the node provided does not have docstrings a TypeError will be raised. If *clean* is `True`, all tabs are expanded to spaces and any whitespace that can be uniformly removed from the second line onwards is removed. """ if not isinstance(node, (AsyncFunctionDef, FunctionDef, ClassDef, Module)): raise TypeError("%r can't have docstrings" % node.__class__.__name__) if not(node.body and isinstance(node.body[0], Expr)): return None node = node.body[0].value if isinstance(node, Constant) and isinstance(node.value, str): text = node.value else: return None if clean: import inspect text = inspect.cleandoc(text) return text _line_pattern = None def _splitlines_no_ff(source, maxlines=None): """Split a string into lines ignoring form feed and other chars. This mimics how the Python parser splits source code. """ global _line_pattern if _line_pattern is None: # lazily computed to speedup import time of `ast` import re _line_pattern = re.compile(r"(.*?(?:\r\n|\n|\r|$))") lines = [] for lineno, match in enumerate(_line_pattern.finditer(source), 1): if maxlines is not None and lineno > maxlines: break lines.append(match[0]) return lines def _pad_whitespace(source): r"""Replace all chars except '\f\t' in a line with spaces.""" result = '' for c in source: if c in '\f\t': result += c else: result += ' ' return result def get_source_segment(source, node, *, padded=False): """Get source code segment of the *source* that generated *node*. If some location information (`lineno`, `end_lineno`, `col_offset`, or `end_col_offset`) is missing, return None. If *padded* is `True`, the first line of a multi-line statement will be padded with spaces to match its original position. """ try: if node.end_lineno is None or node.end_col_offset is None: return None lineno = node.lineno - 1 end_lineno = node.end_lineno - 1 col_offset = node.col_offset end_col_offset = node.end_col_offset except AttributeError: return None lines = _splitlines_no_ff(source, maxlines=end_lineno+1) if end_lineno == lineno: return lines[lineno].encode()[col_offset:end_col_offset].decode() if padded: padding = _pad_whitespace(lines[lineno].encode()[:col_offset].decode()) else: padding = '' first = padding + lines[lineno].encode()[col_offset:].decode() last = lines[end_lineno].encode()[:end_col_offset].decode() lines = lines[lineno+1:end_lineno] lines.insert(0, first) lines.append(last) return ''.join(lines) def walk(node): """ Recursively yield all descendant nodes in the tree starting at *node* (including *node* itself), in no specified order. This is useful if you only want to modify nodes in place and don't care about the context. """ from collections import deque todo = deque([node]) while todo: node = todo.popleft() todo.extend(iter_child_nodes(node)) yield node def compare( a, b, /, *, compare_attributes=False, ): """Recursively compares two ASTs. compare_attributes affects whether AST attributes are considered in the comparison. If compare_attributes is False (default), then attributes are ignored. Otherwise they must all be equal. This option is useful to check whether the ASTs are structurally equal but might differ in whitespace or similar details. """ sentinel = object() # handle the possibility of a missing attribute/field def _compare(a, b): # Compare two fields on an AST object, which may themselves be # AST objects, lists of AST objects, or primitive ASDL types # like identifiers and constants. if isinstance(a, AST): return compare( a, b, compare_attributes=compare_attributes, ) elif isinstance(a, list): # If a field is repeated, then both objects will represent # the value as a list. if len(a) != len(b): return False for a_item, b_item in zip(a, b): if not _compare(a_item, b_item): return False else: return True else: return type(a) is type(b) and a == b def _compare_fields(a, b): if a._fields != b._fields: return False for field in a._fields: a_field = getattr(a, field, sentinel) b_field = getattr(b, field, sentinel) if a_field is sentinel and b_field is sentinel: # both nodes are missing a field at runtime continue if a_field is sentinel or b_field is sentinel: # one of the node is missing a field return False if not _compare(a_field, b_field): return False else: return True def _compare_attributes(a, b): if a._attributes != b._attributes: return False # Attributes are always ints. for attr in a._attributes: a_attr = getattr(a, attr, sentinel) b_attr = getattr(b, attr, sentinel) if a_attr is sentinel and b_attr is sentinel: # both nodes are missing an attribute at runtime continue if a_attr != b_attr: return False else: return True if type(a) is not type(b): return False if not _compare_fields(a, b): return False if compare_attributes and not _compare_attributes(a, b): return False return True class NodeVisitor(object): """ A node visitor base class that walks the abstract syntax tree and calls a visitor function for every node found. This function may return a value which is forwarded by the `visit` method. This class is meant to be subclassed, with the subclass adding visitor methods. Per default the visitor functions for the nodes are ``'visit_'`` + class name of the node. So a `TryFinally` node visit function would be `visit_TryFinally`. This behavior can be changed by overriding the `visit` method. If no visitor function exists for a node (return value `None`) the `generic_visit` visitor is used instead. Don't use the `NodeVisitor` if you want to apply changes to nodes during traversing. For this a special visitor exists (`NodeTransformer`) that allows modifications. """ def visit(self, node): """Visit a node.""" method = 'visit_' + node.__class__.__name__ visitor = getattr(self, method, self.generic_visit) return visitor(node) def generic_visit(self, node): """Called if no explicit visitor function exists for a node.""" for field, value in iter_fields(node): if isinstance(value, list): for item in value: if isinstance(item, AST): self.visit(item) elif isinstance(value, AST): self.visit(value) class NodeTransformer(NodeVisitor): """ A :class:`NodeVisitor` subclass that walks the abstract syntax tree and allows modification of nodes. The `NodeTransformer` will walk the AST and use the return value of the visitor methods to replace or remove the old node. If the return value of the visitor method is ``None``, the node will be removed from its location, otherwise it is replaced with the return value. The return value may be the original node in which case no replacement takes place. Here is an example transformer that rewrites all occurrences of name lookups (``foo``) to ``data['foo']``:: class RewriteName(NodeTransformer): def visit_Name(self, node): return Subscript( value=Name(id='data', ctx=Load()), slice=Constant(value=node.id), ctx=node.ctx ) Keep in mind that if the node you're operating on has child nodes you must either transform the child nodes yourself or call the :meth:`generic_visit` method for the node first. For nodes that were part of a collection of statements (that applies to all statement nodes), the visitor may also return a list of nodes rather than just a single node. Usually you use the transformer like this:: node = YourTransformer().visit(node) """ def generic_visit(self, node): for field, old_value in iter_fields(node): if isinstance(old_value, list): new_values = [] for value in old_value: if isinstance(value, AST): value = self.visit(value) if value is None: continue elif not isinstance(value, AST): new_values.extend(value) continue new_values.append(value) old_value[:] = new_values elif isinstance(old_value, AST): new_node = self.visit(old_value) if new_node is None: delattr(node, field) else: setattr(node, field, new_node) return node class slice(AST): """Deprecated AST node class.""" class Index(slice): """Deprecated AST node class. Use the index value directly instead.""" def __new__(cls, value, **kwargs): return value class ExtSlice(slice): """Deprecated AST node class. Use ast.Tuple instead.""" def __new__(cls, dims=(), **kwargs): return Tuple(list(dims), Load(), **kwargs) # If the ast module is loaded more than once, only add deprecated methods once if not hasattr(Tuple, 'dims'): # The following code is for backward compatibility. # It will be removed in future. def _dims_getter(self): """Deprecated. Use elts instead.""" return self.elts def _dims_setter(self, value): self.elts = value Tuple.dims = property(_dims_getter, _dims_setter) class Suite(mod): """Deprecated AST node class. Unused in Python 3.""" class AugLoad(expr_context): """Deprecated AST node class. Unused in Python 3.""" class AugStore(expr_context): """Deprecated AST node class. Unused in Python 3.""" class Param(expr_context): """Deprecated AST node class. Unused in Python 3.""" def unparse(ast_obj): global _Unparser try: unparser = _Unparser() except NameError: from _ast_unparse import Unparser as _Unparser unparser = _Unparser() return unparser.visit(ast_obj) def main(args=None): import argparse import sys parser = argparse.ArgumentParser(formatter_class=argparse.ArgumentDefaultsHelpFormatter) parser.add_argument('infile', nargs='?', default='-', help='the file to parse; defaults to `stdin`') parser.add_argument('-m', '--mode', default='exec', choices=('exec', 'single', 'eval', 'func_type'), help='specify what kind of code must be parsed') parser.add_argument('--no-type-comments', default=True, action='store_false', help="don't add information about type comments") parser.add_argument('-a', '--include-attributes', action='store_true', help='include attributes such as line numbers and ' 'column offsets') parser.add_argument('-i', '--indent', type=int, default=3, help='indentation of nodes (number of spaces)') parser.add_argument('--feature-version', type=str, default=None, metavar='VERSION', help='Python version in the format `3.x` ' '(for example, `3.10`)') parser.add_argument('-O', '--optimize', type=int, default=-1, metavar='LEVEL', help='optimization level for parser') parser.add_argument('--show-empty', default=False, action='store_true', help='show empty lists and fields in dump output') args = parser.parse_args(args) if args.infile == '-': name = '<stdin>' source = sys.stdin.buffer.read() else: name = args.infile with open(args.infile, 'rb') as infile: source = infile.read() # Process feature_version feature_version = None if args.feature_version: try: major, minor = map(int, args.feature_version.split('.', 1)) except ValueError: parser.error('Invalid format for --feature-version; ' 'expected format 3.x (for example, 3.10)') feature_version = (major, minor) tree = parse(source, name, args.mode, type_comments=args.no_type_comments, feature_version=feature_version, optimize=args.optimize) from _colorize import can_colorize print(dump(tree, include_attributes=args.include_attributes, color=can_colorize(file=sys.stdout), indent=args.indent, show_empty=args.show_empty)) if __name__ == '__main__': main() |
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