"Usage: unparse.py <path to source file>"
from __future__ import print_function, unicode_literals
import six
import sys
import ast
import os
import tokenize
from six import StringIO
# 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:
pass
else:
for x in seq:
inter()
f(x)
class Unparser:
"""Methods in this class recursively traverse an AST and
output source code for the abstract syntax; original formatting
is disregarded. """
def __init__(self, tree, file = sys.stdout, py_ver_consistent=False):
"""Unparser(tree, file=sys.stdout) -> None.
Print the source for tree to file.
Arguments:
py_ver_consistent (bool): if True, generate unparsed code that is
consistent between Python 2.7 and 3.5-3.10.
Consistency is achieved by:
1. Ensuring there are no spaces between unary operators and
their operands.
2. Ensuring that *args and **kwargs are always the last arguments,
regardless of the python version.
3. Always unparsing print as a function.
4. Not putting an extra comma after Python 2 class definitions.
Without these changes, the same source can generate different code for different
Python versions, depending on subtle AST differences.
One place where single source will generate an inconsistent AST is with
multi-argument print statements, e.g.::
print("foo", "bar", "baz")
In Python 2, this prints a tuple; in Python 3, it is the print function with
multiple arguments. Use ``from __future__ import print_function`` to avoid
this inconsistency.
"""
self.f = file
self.future_imports = []
self._indent = 0
self._py_ver_consistent = py_ver_consistent
self.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(six.text_type(text))
def enter(self):
"Print ':', and increase the indentation."
self.write(":")
self._indent += 1
def leave(self):
"Decrease the indentation level."
self._indent -= 1
def dispatch(self, tree):
"Dispatcher function, dispatching tree type T to method _T."
if isinstance(tree, list):
for t in tree:
self.dispatch(t)
return
meth = 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)
def _Interactive(self, tree):
for stmt in tree.body:
self.dispatch(stmt)
def _Expression(self, tree):
self.dispatch(tree.body)
# stmt
def _Expr(self, tree):
self.fill()
self.dispatch(tree.value)
def _NamedExpr(self, tree):
self.write("(")
self.dispatch(tree.target)
self.write(" := ")
self.dispatch(tree.value)
self.write(")")
def _Import(self, t):
self.fill("import ")
interleave(lambda: self.write(", "), self.dispatch, t.names)
def _ImportFrom(self, t):
# A from __future__ import may affect unparsing, so record it.
if t.module and t.module == '__future__':
self.future_imports.extend(n.name for n in t.names)
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 _Exec(self, t):
self.fill("exec ")
self.dispatch(t.body)
if t.globals:
self.write(" in ")
self.dispatch(t.globals)
if t.locals:
self.write(", ")
self.dispatch(t.locals)
def _Print(self, t):
# Use print function so that python 2 unparsing is consistent with 3
if self._py_ver_consistent:
self.fill("print(")
else:
self.fill("print ")
do_comma = False
if t.dest:
self.write(">>")
self.dispatch(t.dest)
do_comma = True
for e in t.values:
if do_comma:self.write(", ")
else:do_comma=True
self.dispatch(e)
if not t.nl:
self.write(",")
if self._py_ver_consistent:
self.write(")")
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 six.PY3:
if not t.exc:
assert not t.cause
return
self.write(" ")
self.dispatch(t.exc)
if t.cause:
self.write(" from ")
self.dispatch(t.cause)
else:
self.write(" ")
if t.type:
self.dispatch(t.type)
if t.inst:
self.write(", ")
self.dispatch(t.inst)
if t.tback:
self.write(", ")
self.dispatch(t.tback)
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 _TryExcept(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()
def _TryFinally(self, t):
if len(t.body) == 1 and isinstance(t.body[0], ast.TryExcept):
# try-except-finally
self.dispatch(t.body)
else:
self.fill("try")
self.enter()
self.dispatch(t.body)
self.leave()
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 ")
if six.PY3:
self.write(t.name)
else:
self.dispatch(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)
if six.PY3:
self.write("(")
comma = False
for e in t.bases:
if comma: self.write(", ")
else: comma = True
self.dispatch(e)
for e in t.keywords:
if comma: self.write(", ")
else: comma = True
self.dispatch(e)
if sys.version_info[:2] < (3, 5):
if t.starargs:
if comma: self.write(", ")
else: comma = True
self.write("*")
self.dispatch(t.starargs)
if t.kwargs:
if comma: self.write(", ")
else: comma = True
self.write("**")
self.dispatch(t.kwargs)
self.write(")")
elif t.bases:
self.write("(")
for a in t.bases[:-1]:
self.dispatch(a)
self.write(", ")
self.dispatch(t.bases[-1])
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 getattr(t, "returns", False):
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 and
isinstance(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 else
if 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 _generic_With(self, t, async_=False):
self.fill("async with " if async_ else "with ")
if hasattr(t, 'items'):
interleave(lambda: self.write(", "), self.dispatch, t.items)
else:
self.dispatch(t.context_expr)
if t.optional_vars:
self.write(" as ")
self.dispatch(t.optional_vars)
self.enter()
self.dispatch(t.body)
self.leave()
def _With(self, t):
self._generic_With(t)
def _AsyncWith(self, t):
self._generic_With(t, async_=True)
# expr
def _Bytes(self, t):
self.write(repr(t.s))
def _Str(self, tree):
if six.PY3:
self.write(repr(tree.s))
else:
# if from __future__ import unicode_literals is in effect,
# then we want to output string literals using a 'b' prefix
# and unicode literals with no prefix.
if "unicode_literals" not in self.future_imports:
self.write(repr(tree.s))
elif isinstance(tree.s, str):
self.write("b" + repr(tree.s))
elif isinstance(tree.s, unicode):
self.write(repr(tree.s).lstrip("u"))
else:
assert False, "shouldn't get here"
def _JoinedStr(self, t):
# JoinedStr(expr* values)
self.write("f")
string = StringIO()
self._fstring_JoinedStr(t, string.write)
# Deviation from `unparse.py`: Try to find an unused quote.
# This change is made to handle _very_ complex f-strings.
v = string.getvalue()
if '\n' in v or '\r' in v:
quote_types = ["'''", '"""']
else:
quote_types = ["'", '"', '"""', "'''"]
for quote_type in quote_types:
if quote_type not in v:
v = "{quote_type}{v}{quote_type}".format(quote_type=quote_type, v=v)
break
else:
v = repr(v)
self.write(v)
def _FormattedValue(self, t):
# FormattedValue(expr value, int? conversion, expr? format_spec)
self.write("f")
string = StringIO()
self._fstring_JoinedStr(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 = 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("!{conversion}".format(conversion=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 _NameConstant(self, t):
self.write(repr(t.value))
def _Repr(self, t):
self.write("`")
self.dispatch(t.value)
self.write("`")
def _write_constant(self, value):
if isinstance(value, (float, complex)):
# Substitute overflowing decimal literal for AST infinities.
self.write(repr(value).replace("inf", INFSTR))
else:
self.write(repr(value))
def _Constant(self, t):
value = t.value
if 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(")")
elif value is Ellipsis: # instead of `...` for Py2 compatibility
self.write("...")
else:
if t.kind == "u":
self.write("u")
self._write_constant(t.value)
def _Num(self, t):
repr_n = repr(t.n)
if six.PY3:
self.write(repr_n.replace("inf", INFSTR))
else:
# Parenthesize negative numbers, to avoid turning (-1)**2 into -1**2.
if repr_n.startswith("-"):
self.write("(")
if "inf" in repr_n and repr_n.endswith("*j"):
repr_n = repr_n.replace("*j", "j")
# Substitute overflowing decimal literal for AST infinities.
self.write(repr_n.replace("inf", INFSTR))
if repr_n.startswith("-"):
self.write(")")
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 getattr(t, 'is_async', False):
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 element
self.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 = item
if k is None:
# for dictionary unpacking operator in dicts {**{'y': 2}}
# see PEP 448 for details
self.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__])
if not self._py_ver_consistent:
self.write(" ")
if six.PY2 and isinstance(t.op, ast.USub) and isinstance(t.operand, ast.Num):
# If we're applying unary minus to a number, parenthesize the number.
# This is necessary: -2147483648 is different from -(2147483648) on
# a 32-bit machine (the first is an int, the second a long), and
# -7j is different from -(7j). (The first has real part 0.0, the second
# has real part -0.0.)
self.write("(")
self.dispatch(t.operand)
self.write(")")
else:
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, getattr(ast, 'Constant', getattr(ast, 'Num', None))) and isinstance(t.value.n, int):
self.write(" ")
self.write(".")
self.write(t.attr)
def _Call(self, t):
self.dispatch(t.func)
self.write("(")
comma = False
# move starred arguments last in Python 3.5+, for consistency w/earlier versions
star_and_kwargs = []
move_stars_last = sys.version_info[:2] >= (3, 5)
for e in t.args:
if move_stars_last and isinstance(e, ast.Starred):
star_and_kwargs.append(e)
else:
if comma: self.write(", ")
else: comma = True
self.dispatch(e)
for e in t.keywords:
# starting from Python 3.5 this denotes a kwargs part of the invocation
if e.arg is None and move_stars_last:
star_and_kwargs.append(e)
else:
if comma: self.write(", ")
else: comma = True
self.dispatch(e)
if move_stars_last:
for e in star_and_kwargs:
if comma: self.write(", ")
else: comma = True
self.dispatch(e)
if sys.version_info[:2] < (3, 5):
if t.starargs:
if comma: self.write(", ")
else: comma = True
self.write("*")
self.dispatch(t.starargs)
if t.kwargs:
if comma: self.write(", ")
else: comma = True
self.write("**")
self.dispatch(t.kwargs)
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)
# slice
def _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)
# argument
def _arg(self, t):
self.write(t.arg)
if t.annotation:
self.write(": ")
self.dispatch(t.annotation)
# others
def _arguments(self, t):
first = True
# normal arguments
all_args = getattr(t, 'posonlyargs', []) + t.args
defaults = [None] * (len(all_args) - len(t.defaults)) + t.defaults
for index, elements in enumerate(zip(all_args, defaults), 1):
a, d = elements
if first:first = False
else: self.write(", ")
self.dispatch(a)
if d:
self.write("=")
self.dispatch(d)
if index == len(getattr(t, 'posonlyargs', ())):
self.write(", /")
# varargs, or bare '*' if no varargs but keyword-only arguments present
if t.vararg or getattr(t, "kwonlyargs", False):
if first:first = False
else: self.write(", ")
self.write("*")
if t.vararg:
if hasattr(t.vararg, 'arg'):
self.write(t.vararg.arg)
if t.vararg.annotation:
self.write(": ")
self.dispatch(t.vararg.annotation)
else:
self.write(t.vararg)
if getattr(t, 'varargannotation', None):
self.write(": ")
self.dispatch(t.varargannotation)
# keyword-only arguments
if getattr(t, "kwonlyargs", False):
for a, d in zip(t.kwonlyargs, t.kw_defaults):
if first:first = False
else: self.write(", ")
self.dispatch(a),
if d:
self.write("=")
self.dispatch(d)
# kwargs
if t.kwarg:
if first:first = False
else: self.write(", ")
if hasattr(t.kwarg, 'arg'):
self.write("**"+t.kwarg.arg)
if t.kwarg.annotation:
self.write(": ")
self.dispatch(t.kwarg.annotation)
else:
self.write("**"+t.kwarg)
if getattr(t, 'kwargannotation', None):
self.write(": ")
self.dispatch(t.kwargannotation)
def _keyword(self, t):
if t.arg is None:
# starting from Python 3.5 this denotes a kwargs part of the invocation
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):
if six.PY3:
with open(filename, "rb") as pyfile:
encoding = tokenize.detect_encoding(pyfile.readline)[0]
with open(filename, "r", encoding=encoding) as pyfile:
source = pyfile.read()
else:
with open(filename, "r") as pyfile:
source = pyfile.read()
tree = compile(source, filename, "exec", ast.PyCF_ONLY_AST, dont_inherit=True)
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 = 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:])
