"Usage: unparse.py <path to source file>"import sysimport astimport tokenizeimport ioimport os# Large float and imaginary literals get turned into infinities in the AST.# We unparse those infinities to INFSTR.INFSTR = "1e" + repr(sys.float_info.max_10_exp + 1)def interleave(inter, f, seq):"""Call f on each item in seq, calling inter() in between."""seq = iter(seq)try:f(next(seq))except StopIteration:passelse:for x in seq:inter()f(x)class Unparser:"""Methods in this class recursively traverse an AST andoutput source code for the abstract syntax; original formattingis disregarded. """def __init__(self, tree, file = sys.stdout):"""Unparser(tree, file=sys.stdout) -> None.Print the source for tree to file."""self.f = fileself._indent = 0self.dispatch(tree)print("", file=self.f)self.f.flush()def fill(self, text = ""):"Indent a piece of text, according to the current indentation level"self.f.write("\n"+" "*self._indent + text)def write(self, text):"Append a piece of text to the current line."self.f.write(text)def enter(self):"Print ':', and increase the indentation."self.write(":")self._indent += 1def leave(self):"Decrease the indentation level."self._indent -= 1def dispatch(self, tree):"Dispatcher function, dispatching tree type T to method _T."if isinstance(tree, list):for t in tree:self.dispatch(t)returnmeth = getattr(self, "_"+tree.__class__.__name__)meth(tree)############### Unparsing methods ####################### There should be one method per concrete grammar type ## Constructors should be grouped by sum type. Ideally, ## this would follow the order in the grammar, but ## currently doesn't. #########################################################def _Module(self, tree):for stmt in tree.body:self.dispatch(stmt)# stmtdef _Expr(self, tree):self.fill()self.dispatch(tree.value)def _Import(self, t):self.fill("import ")interleave(lambda: self.write(", "), self.dispatch, t.names)def _ImportFrom(self, t):self.fill("from ")self.write("." * t.level)if t.module:self.write(t.module)self.write(" import ")interleave(lambda: self.write(", "), self.dispatch, t.names)def _Assign(self, t):self.fill()for target in t.targets:self.dispatch(target)self.write(" = ")self.dispatch(t.value)def _AugAssign(self, t):self.fill()self.dispatch(t.target)self.write(" "+self.binop[t.op.__class__.__name__]+"= ")self.dispatch(t.value)def _AnnAssign(self, t):self.fill()if not t.simple and isinstance(t.target, ast.Name):self.write('(')self.dispatch(t.target)if not t.simple and isinstance(t.target, ast.Name):self.write(')')self.write(": ")self.dispatch(t.annotation)if t.value:self.write(" = ")self.dispatch(t.value)def _Return(self, t):self.fill("return")if t.value:self.write(" ")self.dispatch(t.value)def _Pass(self, t):self.fill("pass")def _Break(self, t):self.fill("break")def _Continue(self, t):self.fill("continue")def _Delete(self, t):self.fill("del ")interleave(lambda: self.write(", "), self.dispatch, t.targets)def _Assert(self, t):self.fill("assert ")self.dispatch(t.test)if t.msg:self.write(", ")self.dispatch(t.msg)def _Global(self, t):self.fill("global ")interleave(lambda: self.write(", "), self.write, t.names)def _Nonlocal(self, t):self.fill("nonlocal ")interleave(lambda: self.write(", "), self.write, t.names)def _Await(self, t):self.write("(")self.write("await")if t.value:self.write(" ")self.dispatch(t.value)self.write(")")def _Yield(self, t):self.write("(")self.write("yield")if t.value:self.write(" ")self.dispatch(t.value)self.write(")")def _YieldFrom(self, t):self.write("(")self.write("yield from")if t.value:self.write(" ")self.dispatch(t.value)self.write(")")def _Raise(self, t):self.fill("raise")if not t.exc:assert not t.causereturnself.write(" ")self.dispatch(t.exc)if t.cause:self.write(" from ")self.dispatch(t.cause)def _Try(self, t):self.fill("try")self.enter()self.dispatch(t.body)self.leave()for ex in t.handlers:self.dispatch(ex)if t.orelse:self.fill("else")self.enter()self.dispatch(t.orelse)self.leave()if t.finalbody:self.fill("finally")self.enter()self.dispatch(t.finalbody)self.leave()def _ExceptHandler(self, t):self.fill("except")if t.type:self.write(" ")self.dispatch(t.type)if t.name:self.write(" as ")self.write(t.name)self.enter()self.dispatch(t.body)self.leave()def _ClassDef(self, t):self.write("\n")for deco in t.decorator_list:self.fill("@")self.dispatch(deco)self.fill("class "+t.name)self.write("(")comma = Falsefor e in t.bases:if comma: self.write(", ")else: comma = Trueself.dispatch(e)for e in t.keywords:if comma: self.write(", ")else: comma = Trueself.dispatch(e)self.write(")")self.enter()self.dispatch(t.body)self.leave()def _FunctionDef(self, t):self.__FunctionDef_helper(t, "def")def _AsyncFunctionDef(self, t):self.__FunctionDef_helper(t, "async def")def __FunctionDef_helper(self, t, fill_suffix):self.write("\n")for deco in t.decorator_list:self.fill("@")self.dispatch(deco)def_str = fill_suffix+" "+t.name + "("self.fill(def_str)self.dispatch(t.args)self.write(")")if t.returns:self.write(" -> ")self.dispatch(t.returns)self.enter()self.dispatch(t.body)self.leave()def _For(self, t):self.__For_helper("for ", t)def _AsyncFor(self, t):self.__For_helper("async for ", t)def __For_helper(self, fill, t):self.fill(fill)self.dispatch(t.target)self.write(" in ")self.dispatch(t.iter)self.enter()self.dispatch(t.body)self.leave()if t.orelse:self.fill("else")self.enter()self.dispatch(t.orelse)self.leave()def _If(self, t):self.fill("if ")self.dispatch(t.test)self.enter()self.dispatch(t.body)self.leave()# collapse nested ifs into equivalent elifs.while (t.orelse and len(t.orelse) == 1 andisinstance(t.orelse[0], ast.If)):t = t.orelse[0]self.fill("elif ")self.dispatch(t.test)self.enter()self.dispatch(t.body)self.leave()# final elseif t.orelse:self.fill("else")self.enter()self.dispatch(t.orelse)self.leave()def _While(self, t):self.fill("while ")self.dispatch(t.test)self.enter()self.dispatch(t.body)self.leave()if t.orelse:self.fill("else")self.enter()self.dispatch(t.orelse)self.leave()def _With(self, t):self.fill("with ")interleave(lambda: self.write(", "), self.dispatch, t.items)self.enter()self.dispatch(t.body)self.leave()def _AsyncWith(self, t):self.fill("async with ")interleave(lambda: self.write(", "), self.dispatch, t.items)self.enter()self.dispatch(t.body)self.leave()# exprdef _Bytes(self, t):self.write(repr(t.s))def _Str(self, tree):self.write(repr(tree.s))def _JoinedStr(self, t):self.write("f")string = io.StringIO()self._fstring_JoinedStr(t, string.write)self.write(repr(string.getvalue()))def _FormattedValue(self, t):self.write("f")string = io.StringIO()self._fstring_FormattedValue(t, string.write)self.write(repr(string.getvalue()))def _fstring_JoinedStr(self, t, write):for value in t.values:meth = getattr(self, "_fstring_" + type(value).__name__)meth(value, write)def _fstring_Str(self, t, write):value = t.s.replace("{", "{{").replace("}", "}}")write(value)def _fstring_Constant(self, t, write):assert isinstance(t.value, str)value = t.value.replace("{", "{{").replace("}", "}}")write(value)def _fstring_FormattedValue(self, t, write):write("{")expr = io.StringIO()Unparser(t.value, expr)expr = expr.getvalue().rstrip("\n")if expr.startswith("{"):write(" ") # Separate pair of opening brackets as "{ {"write(expr)if t.conversion != -1:conversion = chr(t.conversion)assert conversion in "sra"write(f"!{conversion}")if t.format_spec:write(":")meth = getattr(self, "_fstring_" + type(t.format_spec).__name__)meth(t.format_spec, write)write("}")def _Name(self, t):self.write(t.id)def _write_constant(self, value):if isinstance(value, (float, complex)):self.write(repr(value).replace("inf", INFSTR))else:self.write(repr(value))def _Constant(self, t):value = t.valueif isinstance(value, tuple):self.write("(")if len(value) == 1:self._write_constant(value[0])self.write(",")else:interleave(lambda: self.write(", "), self._write_constant, value)self.write(")")else:self._write_constant(t.value)def _NameConstant(self, t):self.write(repr(t.value))def _Num(self, t):# Substitute overflowing decimal literal for AST infinities.self.write(repr(t.n).replace("inf", INFSTR))def _List(self, t):self.write("[")interleave(lambda: self.write(", "), self.dispatch, t.elts)self.write("]")def _ListComp(self, t):self.write("[")self.dispatch(t.elt)for gen in t.generators:self.dispatch(gen)self.write("]")def _GeneratorExp(self, t):self.write("(")self.dispatch(t.elt)for gen in t.generators:self.dispatch(gen)self.write(")")def _SetComp(self, t):self.write("{")self.dispatch(t.elt)for gen in t.generators:self.dispatch(gen)self.write("}")def _DictComp(self, t):self.write("{")self.dispatch(t.key)self.write(": ")self.dispatch(t.value)for gen in t.generators:self.dispatch(gen)self.write("}")def _comprehension(self, t):if t.is_async:self.write(" async for ")else:self.write(" for ")self.dispatch(t.target)self.write(" in ")self.dispatch(t.iter)for if_clause in t.ifs:self.write(" if ")self.dispatch(if_clause)def _IfExp(self, t):self.write("(")self.dispatch(t.body)self.write(" if ")self.dispatch(t.test)self.write(" else ")self.dispatch(t.orelse)self.write(")")def _Set(self, t):assert(t.elts) # should be at least one elementself.write("{")interleave(lambda: self.write(", "), self.dispatch, t.elts)self.write("}")def _Dict(self, t):self.write("{")def write_key_value_pair(k, v):self.dispatch(k)self.write(": ")self.dispatch(v)def write_item(item):k, v = itemif k is None:# for dictionary unpacking operator in dicts {**{'y': 2}}# see PEP 448 for detailsself.write("**")self.dispatch(v)else:write_key_value_pair(k, v)interleave(lambda: self.write(", "), write_item, zip(t.keys, t.values))self.write("}")def _Tuple(self, t):self.write("(")if len(t.elts) == 1:elt = t.elts[0]self.dispatch(elt)self.write(",")else:interleave(lambda: self.write(", "), self.dispatch, t.elts)self.write(")")unop = {"Invert":"~", "Not": "not", "UAdd":"+", "USub":"-"}def _UnaryOp(self, t):self.write("(")self.write(self.unop[t.op.__class__.__name__])self.write(" ")self.dispatch(t.operand)self.write(")")binop = { "Add":"+", "Sub":"-", "Mult":"*", "MatMult":"@", "Div":"/", "Mod":"%","LShift":"<<", "RShift":">>", "BitOr":"|", "BitXor":"^", "BitAnd":"&","FloorDiv":"//", "Pow": "**"}def _BinOp(self, t):self.write("(")self.dispatch(t.left)self.write(" " + self.binop[t.op.__class__.__name__] + " ")self.dispatch(t.right)self.write(")")cmpops = {"Eq":"==", "NotEq":"!=", "Lt":"<", "LtE":"<=", "Gt":">", "GtE":">=","Is":"is", "IsNot":"is not", "In":"in", "NotIn":"not in"}def _Compare(self, t):self.write("(")self.dispatch(t.left)for o, e in zip(t.ops, t.comparators):self.write(" " + self.cmpops[o.__class__.__name__] + " ")self.dispatch(e)self.write(")")boolops = {ast.And: 'and', ast.Or: 'or'}def _BoolOp(self, t):self.write("(")s = " %s " % self.boolops[t.op.__class__]interleave(lambda: self.write(s), self.dispatch, t.values)self.write(")")def _Attribute(self,t):self.dispatch(t.value)# Special case: 3.__abs__() is a syntax error, so if t.value# is an integer literal then we need to either parenthesize# it or add an extra space to get 3 .__abs__().if ((isinstance(t.value, ast.Num) and isinstance(t.value.n, int))or (isinstance(t.value, ast.Constant) and isinstance(t.value.value, int))):self.write(" ")self.write(".")self.write(t.attr)def _Call(self, t):self.dispatch(t.func)self.write("(")comma = Falsefor e in t.args:if comma: self.write(", ")else: comma = Trueself.dispatch(e)for e in t.keywords:if comma: self.write(", ")else: comma = Trueself.dispatch(e)self.write(")")def _Subscript(self, t):self.dispatch(t.value)self.write("[")self.dispatch(t.slice)self.write("]")def _Starred(self, t):self.write("*")self.dispatch(t.value)# slicedef _Ellipsis(self, t):self.write("...")def _Index(self, t):self.dispatch(t.value)def _Slice(self, t):if t.lower:self.dispatch(t.lower)self.write(":")if t.upper:self.dispatch(t.upper)if t.step:self.write(":")self.dispatch(t.step)def _ExtSlice(self, t):interleave(lambda: self.write(', '), self.dispatch, t.dims)# argumentdef _arg(self, t):self.write(t.arg)if t.annotation:self.write(": ")self.dispatch(t.annotation)# othersdef _arguments(self, t):first = True# normal argumentsdefaults = [None] * (len(t.args) - len(t.defaults)) + t.defaultsfor a, d in zip(t.args, defaults):if first:first = Falseelse: self.write(", ")self.dispatch(a)if d:self.write("=")self.dispatch(d)# varargs, or bare '*' if no varargs but keyword-only arguments presentif t.vararg or t.kwonlyargs:if first:first = Falseelse: self.write(", ")self.write("*")if t.vararg:self.write(t.vararg.arg)if t.vararg.annotation:self.write(": ")self.dispatch(t.vararg.annotation)# keyword-only argumentsif t.kwonlyargs:for a, d in zip(t.kwonlyargs, t.kw_defaults):if first:first = Falseelse: self.write(", ")self.dispatch(a),if d:self.write("=")self.dispatch(d)# kwargsif t.kwarg:if first:first = Falseelse: self.write(", ")self.write("**"+t.kwarg.arg)if t.kwarg.annotation:self.write(": ")self.dispatch(t.kwarg.annotation)def _keyword(self, t):if t.arg is None:self.write("**")else:self.write(t.arg)self.write("=")self.dispatch(t.value)def _Lambda(self, t):self.write("(")self.write("lambda ")self.dispatch(t.args)self.write(": ")self.dispatch(t.body)self.write(")")def _alias(self, t):self.write(t.name)if t.asname:self.write(" as "+t.asname)def _withitem(self, t):self.dispatch(t.context_expr)if t.optional_vars:self.write(" as ")self.dispatch(t.optional_vars)def roundtrip(filename, output=sys.stdout):with open(filename, "rb") as pyfile:encoding = tokenize.detect_encoding(pyfile.readline)[0]with open(filename, "r", encoding=encoding) as pyfile:source = pyfile.read()tree = compile(source, filename, "exec", ast.PyCF_ONLY_AST)Unparser(tree, output)def testdir(a):try:names = [n for n in os.listdir(a) if n.endswith('.py')]except OSError:print("Directory not readable: %s" % a, file=sys.stderr)else:for n in names:fullname = os.path.join(a, n)if os.path.isfile(fullname):output = io.StringIO()print('Testing %s' % fullname)try:roundtrip(fullname, output)except Exception as e:print(' Failed to compile, exception is %s' % repr(e))elif os.path.isdir(fullname):testdir(fullname)def main(args):if args[0] == '--testdir':for a in args[1:]:testdir(a)else:for a in args:roundtrip(a)if __name__=='__main__':main(sys.argv[1:])
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