"Usage: unparse.py <path to source file>"

import sys

import ast

import tokenize

import io

import 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:

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):

"""Unparser(tree, file=sys.stdout) -> None.

Print the source for tree to file."""

self.f = file

self._indent = 0

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(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)

# 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):

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.cause

return

self.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 = 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)

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 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 _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()

# expr

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_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)):

# 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 ...:

self.write("...")

else:

if t.kind == "u":

self.write("u")

self._write_constant(t.value)

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 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__])

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.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 = False

for e in t.args:

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)

self.write(")")

def _Subscript(self, t):

self.dispatch(t.value)

self.write("[")

if (isinstance(t.slice, ast.Index)

and isinstance(t.slice.value, ast.Tuple)

and t.slice.value.elts):

if len(t.slice.value.elts) == 1:

elt = t.slice.value.elts[0]

self.dispatch(elt)

self.write(",")

else:

interleave(lambda: self.write(", "), self.dispatch, t.slice.value.elts)

else:

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):

if len(t.dims) == 1:

elt = t.dims[0]

self.dispatch(elt)

self.write(",")

else:

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 = 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(t.posonlyargs):

self.write(", /")

# varargs, or bare '*' if no varargs but keyword-only arguments present

if t.vararg or t.kwonlyargs:

if first:first = False

else: 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 arguments

if t.kwonlyargs:

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(", ")

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:])