bpo-38870: Expose a function to unparse an ast object in the ast module (GH-17302)

Add ast.unparse() as a function in the ast module that can be used to unparse an
ast.AST object and produce a string with code that would produce an equivalent ast.AST
object when parsed.
This commit is contained in:
Pablo Galindo 2019-11-24 23:02:40 +00:00 committed by GitHub
parent 6bf644ec82
commit 27fc3b6f3f
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6 changed files with 772 additions and 751 deletions

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@ -161,6 +161,19 @@ and classes for traversing abstract syntax trees:
Added ``type_comments``, ``mode='func_type'`` and ``feature_version``.
.. function:: unparse(ast_obj)
Unparse an :class:`ast.AST` object and generate a string with code
that would produce an equivalent :class:`ast.AST` object if parsed
back with :func:`ast.parse`.
.. warning::
The produced code string will not necesarily be equal to the original
code that generated the :class:`ast.AST` object.
.. versionadded:: 3.9
.. function:: literal_eval(node_or_string)
Safely evaluate an expression node or a string containing a Python literal or

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@ -121,6 +121,11 @@ Added the *indent* option to :func:`~ast.dump` which allows it to produce a
multiline indented output.
(Contributed by Serhiy Storchaka in :issue:`37995`.)
Added the :func:`ast.unparse` as a function in the :mod:`ast` module that can
be used to unparse an :class:`ast.AST` object and produce a string with code
that would produce an equivalent :class:`ast.AST` object when parsed.
(Contributed by Pablo Galindo and Batuhan Taskaya in :issue:`38870`.)
asyncio
-------

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@ -24,7 +24,9 @@
:copyright: Copyright 2008 by Armin Ronacher.
:license: Python License.
"""
import sys
from _ast import *
from contextlib import contextmanager
def parse(source, filename='<unknown>', mode='exec', *,
@ -551,6 +553,697 @@ def __new__(cls, *args, **kwargs):
type(...): 'Ellipsis',
}
# 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)
class _Unparser(NodeVisitor):
"""Methods in this class recursively traverse an AST and
output source code for the abstract syntax; original formatting
is disregarded."""
def __init__(self):
self._source = []
self._buffer = []
self._indent = 0
def interleave(self, 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)
def fill(self, text=""):
"""Indent a piece of text and append it, according to the current
indentation level"""
self.write("\n" + " " * self._indent + text)
def write(self, text):
"""Append a piece of text"""
self._source.append(text)
def buffer_writer(self, text):
self._buffer.append(text)
@property
def buffer(self):
value = "".join(self._buffer)
self._buffer.clear()
return value
@contextmanager
def block(self):
"""A context manager for preparing the source for blocks. It adds
the character':', increases the indentation on enter and decreases
the indentation on exit."""
self.write(":")
self._indent += 1
yield
self._indent -= 1
def traverse(self, node):
if isinstance(node, list):
for item in node:
self.traverse(item)
else:
super().visit(node)
def visit(self, node):
"""Outputs a source code string that, if converted back to an ast
(using ast.parse) will generate an AST equivalent to *node*"""
self._source = []
self.traverse(node)
return "".join(self._source)
def visit_Module(self, node):
for subnode in node.body:
self.traverse(subnode)
def visit_Expr(self, node):
self.fill()
self.traverse(node.value)
def visit_NamedExpr(self, node):
self.write("(")
self.traverse(node.target)
self.write(" := ")
self.traverse(node.value)
self.write(")")
def visit_Import(self, node):
self.fill("import ")
self.interleave(lambda: self.write(", "), self.traverse, node.names)
def visit_ImportFrom(self, node):
self.fill("from ")
self.write("." * node.level)
if node.module:
self.write(node.module)
self.write(" import ")
self.interleave(lambda: self.write(", "), self.traverse, node.names)
def visit_Assign(self, node):
self.fill()
for target in node.targets:
self.traverse(target)
self.write(" = ")
self.traverse(node.value)
def visit_AugAssign(self, node):
self.fill()
self.traverse(node.target)
self.write(" " + self.binop[node.op.__class__.__name__] + "= ")
self.traverse(node.value)
def visit_AnnAssign(self, node):
self.fill()
if not node.simple and isinstance(node.target, Name):
self.write("(")
self.traverse(node.target)
if not node.simple and isinstance(node.target, Name):
self.write(")")
self.write(": ")
self.traverse(node.annotation)
if node.value:
self.write(" = ")
self.traverse(node.value)
def visit_Return(self, node):
self.fill("return")
if node.value:
self.write(" ")
self.traverse(node.value)
def visit_Pass(self, node):
self.fill("pass")
def visit_Break(self, node):
self.fill("break")
def visit_Continue(self, node):
self.fill("continue")
def visit_Delete(self, node):
self.fill("del ")
self.interleave(lambda: self.write(", "), self.traverse, node.targets)
def visit_Assert(self, node):
self.fill("assert ")
self.traverse(node.test)
if node.msg:
self.write(", ")
self.traverse(node.msg)
def visit_Global(self, node):
self.fill("global ")
self.interleave(lambda: self.write(", "), self.write, node.names)
def visit_Nonlocal(self, node):
self.fill("nonlocal ")
self.interleave(lambda: self.write(", "), self.write, node.names)
def visit_Await(self, node):
self.write("(")
self.write("await")
if node.value:
self.write(" ")
self.traverse(node.value)
self.write(")")
def visit_Yield(self, node):
self.write("(")
self.write("yield")
if node.value:
self.write(" ")
self.traverse(node.value)
self.write(")")
def visit_YieldFrom(self, node):
self.write("(")
self.write("yield from")
if node.value:
self.write(" ")
self.traverse(node.value)
self.write(")")
def visit_Raise(self, node):
self.fill("raise")
if not node.exc:
if node.cause:
raise ValueError(f"Node can't use cause without an exception.")
return
self.write(" ")
self.traverse(node.exc)
if node.cause:
self.write(" from ")
self.traverse(node.cause)
def visit_Try(self, node):
self.fill("try")
with self.block():
self.traverse(node.body)
for ex in node.handlers:
self.traverse(ex)
if node.orelse:
self.fill("else")
with self.block():
self.traverse(node.orelse)
if node.finalbody:
self.fill("finally")
with self.block():
self.traverse(node.finalbody)
def visit_ExceptHandler(self, node):
self.fill("except")
if node.type:
self.write(" ")
self.traverse(node.type)
if node.name:
self.write(" as ")
self.write(node.name)
with self.block():
self.traverse(node.body)
def visit_ClassDef(self, node):
self.write("\n")
for deco in node.decorator_list:
self.fill("@")
self.traverse(deco)
self.fill("class " + node.name)
self.write("(")
comma = False
for e in node.bases:
if comma:
self.write(", ")
else:
comma = True
self.traverse(e)
for e in node.keywords:
if comma:
self.write(", ")
else:
comma = True
self.traverse(e)
self.write(")")
with self.block():
self.traverse(node.body)
def visit_FunctionDef(self, node):
self.__FunctionDef_helper(node, "def")
def visit_AsyncFunctionDef(self, node):
self.__FunctionDef_helper(node, "async def")
def __FunctionDef_helper(self, node, fill_suffix):
self.write("\n")
for deco in node.decorator_list:
self.fill("@")
self.traverse(deco)
def_str = fill_suffix + " " + node.name + "("
self.fill(def_str)
self.traverse(node.args)
self.write(")")
if node.returns:
self.write(" -> ")
self.traverse(node.returns)
with self.block():
self.traverse(node.body)
def visit_For(self, node):
self.__For_helper("for ", node)
def visit_AsyncFor(self, node):
self.__For_helper("async for ", node)
def __For_helper(self, fill, node):
self.fill(fill)
self.traverse(node.target)
self.write(" in ")
self.traverse(node.iter)
with self.block():
self.traverse(node.body)
if node.orelse:
self.fill("else")
with self.block():
self.traverse(node.orelse)
def visit_If(self, node):
self.fill("if ")
self.traverse(node.test)
with self.block():
self.traverse(node.body)
# collapse nested ifs into equivalent elifs.
while node.orelse and len(node.orelse) == 1 and isinstance(node.orelse[0], If):
node = node.orelse[0]
self.fill("elif ")
self.traverse(node.test)
with self.block():
self.traverse(node.body)
# final else
if node.orelse:
self.fill("else")
with self.block():
self.traverse(node.orelse)
def visit_While(self, node):
self.fill("while ")
self.traverse(node.test)
with self.block():
self.traverse(node.body)
if node.orelse:
self.fill("else")
with self.block():
self.traverse(node.orelse)
def visit_With(self, node):
self.fill("with ")
self.interleave(lambda: self.write(", "), self.traverse, node.items)
with self.block():
self.traverse(node.body)
def visit_AsyncWith(self, node):
self.fill("async with ")
self.interleave(lambda: self.write(", "), self.traverse, node.items)
with self.block():
self.traverse(node.body)
def visit_JoinedStr(self, node):
self.write("f")
self._fstring_JoinedStr(node, self.buffer_writer)
self.write(repr(self.buffer))
def visit_FormattedValue(self, node):
self.write("f")
self._fstring_FormattedValue(node, self.buffer_writer)
self.write(repr(self.buffer))
def _fstring_JoinedStr(self, node, write):
for value in node.values:
meth = getattr(self, "_fstring_" + type(value).__name__)
meth(value, write)
def _fstring_Constant(self, node, write):
if not isinstance(node.value, str):
raise ValueError("Constants inside JoinedStr should be a string.")
value = node.value.replace("{", "{{").replace("}", "}}")
write(value)
def _fstring_FormattedValue(self, node, write):
write("{")
expr = type(self)().visit(node.value).rstrip("\n")
if expr.startswith("{"):
write(" ") # Separate pair of opening brackets as "{ {"
write(expr)
if node.conversion != -1:
conversion = chr(node.conversion)
if conversion not in "sra":
raise ValueError("Unknown f-string conversion.")
write(f"!{conversion}")
if node.format_spec:
write(":")
meth = getattr(self, "_fstring_" + type(node.format_spec).__name__)
meth(node.format_spec, write)
write("}")
def visit_Name(self, node):
self.write(node.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 visit_Constant(self, node):
value = node.value
if isinstance(value, tuple):
self.write("(")
if len(value) == 1:
self._write_constant(value[0])
self.write(",")
else:
self.interleave(lambda: self.write(", "), self._write_constant, value)
self.write(")")
elif value is ...:
self.write("...")
else:
if node.kind == "u":
self.write("u")
self._write_constant(node.value)
def visit_List(self, node):
self.write("[")
self.interleave(lambda: self.write(", "), self.traverse, node.elts)
self.write("]")
def visit_ListComp(self, node):
self.write("[")
self.traverse(node.elt)
for gen in node.generators:
self.traverse(gen)
self.write("]")
def visit_GeneratorExp(self, node):
self.write("(")
self.traverse(node.elt)
for gen in node.generators:
self.traverse(gen)
self.write(")")
def visit_SetComp(self, node):
self.write("{")
self.traverse(node.elt)
for gen in node.generators:
self.traverse(gen)
self.write("}")
def visit_DictComp(self, node):
self.write("{")
self.traverse(node.key)
self.write(": ")
self.traverse(node.value)
for gen in node.generators:
self.traverse(gen)
self.write("}")
def visit_comprehension(self, node):
if node.is_async:
self.write(" async for ")
else:
self.write(" for ")
self.traverse(node.target)
self.write(" in ")
self.traverse(node.iter)
for if_clause in node.ifs:
self.write(" if ")
self.traverse(if_clause)
def visit_IfExp(self, node):
self.write("(")
self.traverse(node.body)
self.write(" if ")
self.traverse(node.test)
self.write(" else ")
self.traverse(node.orelse)
self.write(")")
def visit_Set(self, node):
if not node.elts:
raise ValueError("Set node should has at least one item")
self.write("{")
self.interleave(lambda: self.write(", "), self.traverse, node.elts)
self.write("}")
def visit_Dict(self, node):
self.write("{")
def write_key_value_pair(k, v):
self.traverse(k)
self.write(": ")
self.traverse(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.traverse(v)
else:
write_key_value_pair(k, v)
self.interleave(
lambda: self.write(", "), write_item, zip(node.keys, node.values)
)
self.write("}")
def visit_Tuple(self, node):
self.write("(")
if len(node.elts) == 1:
elt = node.elts[0]
self.traverse(elt)
self.write(",")
else:
self.interleave(lambda: self.write(", "), self.traverse, node.elts)
self.write(")")
unop = {"Invert": "~", "Not": "not", "UAdd": "+", "USub": "-"}
def visit_UnaryOp(self, node):
self.write("(")
self.write(self.unop[node.op.__class__.__name__])
self.write(" ")
self.traverse(node.operand)
self.write(")")
binop = {
"Add": "+",
"Sub": "-",
"Mult": "*",
"MatMult": "@",
"Div": "/",
"Mod": "%",
"LShift": "<<",
"RShift": ">>",
"BitOr": "|",
"BitXor": "^",
"BitAnd": "&",
"FloorDiv": "//",
"Pow": "**",
}
def visit_BinOp(self, node):
self.write("(")
self.traverse(node.left)
self.write(" " + self.binop[node.op.__class__.__name__] + " ")
self.traverse(node.right)
self.write(")")
cmpops = {
"Eq": "==",
"NotEq": "!=",
"Lt": "<",
"LtE": "<=",
"Gt": ">",
"GtE": ">=",
"Is": "is",
"IsNot": "is not",
"In": "in",
"NotIn": "not in",
}
def visit_Compare(self, node):
self.write("(")
self.traverse(node.left)
for o, e in zip(node.ops, node.comparators):
self.write(" " + self.cmpops[o.__class__.__name__] + " ")
self.traverse(e)
self.write(")")
boolops = {And: "and", Or: "or"}
def visit_BoolOp(self, node):
self.write("(")
s = " %s " % self.boolops[node.op.__class__]
self.interleave(lambda: self.write(s), self.traverse, node.values)
self.write(")")
def visit_Attribute(self, node):
self.traverse(node.value)
# Special case: 3.__abs__() is a syntax error, so if node.value
# is an integer literal then we need to either parenthesize
# it or add an extra space to get 3 .__abs__().
if isinstance(node.value, Constant) and isinstance(node.value.value, int):
self.write(" ")
self.write(".")
self.write(node.attr)
def visit_Call(self, node):
self.traverse(node.func)
self.write("(")
comma = False
for e in node.args:
if comma:
self.write(", ")
else:
comma = True
self.traverse(e)
for e in node.keywords:
if comma:
self.write(", ")
else:
comma = True
self.traverse(e)
self.write(")")
def visit_Subscript(self, node):
self.traverse(node.value)
self.write("[")
self.traverse(node.slice)
self.write("]")
def visit_Starred(self, node):
self.write("*")
self.traverse(node.value)
def visit_Ellipsis(self, node):
self.write("...")
def visit_Index(self, node):
self.traverse(node.value)
def visit_Slice(self, node):
if node.lower:
self.traverse(node.lower)
self.write(":")
if node.upper:
self.traverse(node.upper)
if node.step:
self.write(":")
self.traverse(node.step)
def visit_ExtSlice(self, node):
self.interleave(lambda: self.write(", "), self.traverse, node.dims)
def visit_arg(self, node):
self.write(node.arg)
if node.annotation:
self.write(": ")
self.traverse(node.annotation)
def visit_arguments(self, node):
first = True
# normal arguments
all_args = node.posonlyargs + node.args
defaults = [None] * (len(all_args) - len(node.defaults)) + node.defaults
for index, elements in enumerate(zip(all_args, defaults), 1):
a, d = elements
if first:
first = False
else:
self.write(", ")
self.traverse(a)
if d:
self.write("=")
self.traverse(d)
if index == len(node.posonlyargs):
self.write(", /")
# varargs, or bare '*' if no varargs but keyword-only arguments present
if node.vararg or node.kwonlyargs:
if first:
first = False
else:
self.write(", ")
self.write("*")
if node.vararg:
self.write(node.vararg.arg)
if node.vararg.annotation:
self.write(": ")
self.traverse(node.vararg.annotation)
# keyword-only arguments
if node.kwonlyargs:
for a, d in zip(node.kwonlyargs, node.kw_defaults):
if first:
first = False
else:
self.write(", ")
self.traverse(a),
if d:
self.write("=")
self.traverse(d)
# kwargs
if node.kwarg:
if first:
first = False
else:
self.write(", ")
self.write("**" + node.kwarg.arg)
if node.kwarg.annotation:
self.write(": ")
self.traverse(node.kwarg.annotation)
def visit_keyword(self, node):
if node.arg is None:
self.write("**")
else:
self.write(node.arg)
self.write("=")
self.traverse(node.value)
def visit_Lambda(self, node):
self.write("(")
self.write("lambda ")
self.traverse(node.args)
self.write(": ")
self.traverse(node.body)
self.write(")")
def visit_alias(self, node):
self.write(node.name)
if node.asname:
self.write(" as " + node.asname)
def visit_withitem(self, node):
self.traverse(node.context_expr)
if node.optional_vars:
self.write(" as ")
self.traverse(node.optional_vars)
def unparse(ast_obj):
unparser = _Unparser()
return unparser.visit(ast_obj)
def main():
import argparse

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@ -3,19 +3,12 @@
import unittest
import test.support
import io
import os
import pathlib
import random
import tokenize
import ast
import functools
from test.test_tools import basepath, toolsdir, skip_if_missing
skip_if_missing()
parser_path = os.path.join(toolsdir, "parser")
with test.support.DirsOnSysPath(parser_path):
import unparse
def read_pyfile(filename):
"""Read and return the contents of a Python source file (as a
@ -26,6 +19,7 @@ def read_pyfile(filename):
source = pyfile.read()
return source
for_else = """\
def f():
for x in range(10):
@ -119,18 +113,21 @@ class Foo: pass
suite1
"""
class ASTTestCase(unittest.TestCase):
def assertASTEqual(self, ast1, ast2):
self.assertEqual(ast.dump(ast1), ast.dump(ast2))
def check_roundtrip(self, code1, filename="internal"):
ast1 = compile(code1, filename, "exec", ast.PyCF_ONLY_AST)
unparse_buffer = io.StringIO()
unparse.Unparser(ast1, unparse_buffer)
code2 = unparse_buffer.getvalue()
ast2 = compile(code2, filename, "exec", ast.PyCF_ONLY_AST)
def check_roundtrip(self, code1):
ast1 = ast.parse(code1)
code2 = ast.unparse(ast1)
ast2 = ast.parse(code2)
self.assertASTEqual(ast1, ast2)
def check_invalid(self, node, raises=ValueError):
self.assertRaises(raises, ast.unparse, node)
class UnparseTestCase(ASTTestCase):
# Tests for specific bugs found in earlier versions of unparse
@ -174,8 +171,8 @@ def test_huge_float(self):
self.check_roundtrip("-1e1000j")
def test_min_int(self):
self.check_roundtrip(str(-2**31))
self.check_roundtrip(str(-2**63))
self.check_roundtrip(str(-(2 ** 31)))
self.check_roundtrip(str(-(2 ** 63)))
def test_imaginary_literals(self):
self.check_roundtrip("7j")
@ -265,54 +262,67 @@ def test_dict_unpacking_in_dict(self):
self.check_roundtrip(r"""{**{'y': 2}, 'x': 1}""")
self.check_roundtrip(r"""{**{'y': 2}, **{'x': 1}}""")
def test_invalid_raise(self):
self.check_invalid(ast.Raise(exc=None, cause=ast.Name(id="X")))
def test_invalid_fstring_constant(self):
self.check_invalid(ast.JoinedStr(values=[ast.Constant(value=100)]))
def test_invalid_fstring_conversion(self):
self.check_invalid(
ast.FormattedValue(
value=ast.Constant(value="a", kind=None),
conversion=ord("Y"), # random character
format_spec=None,
)
)
def test_invalid_set(self):
self.check_invalid(ast.Set(elts=[]))
class DirectoryTestCase(ASTTestCase):
"""Test roundtrip behaviour on all files in Lib and Lib/test."""
NAMES = None
# test directories, relative to the root of the distribution
test_directories = 'Lib', os.path.join('Lib', 'test')
lib_dir = pathlib.Path(__file__).parent / ".."
test_directories = (lib_dir, lib_dir / "test")
skip_files = {"test_fstring.py"}
@classmethod
def get_names(cls):
if cls.NAMES is not None:
return cls.NAMES
@functools.cached_property
def files_to_test(self):
# bpo-31174: Use cached_property to store the names sample
# to always test the same files. It prevents false alarms
# when hunting reference leaks.
names = []
for d in cls.test_directories:
test_dir = os.path.join(basepath, d)
for n in os.listdir(test_dir):
if n.endswith('.py') and not n.startswith('bad'):
names.append(os.path.join(test_dir, n))
items = [
item.resolve()
for directory in self.test_directories
for item in directory.glob("*.py")
if not item.name.startswith("bad")
]
# Test limited subset of files unless the 'cpu' resource is specified.
if not test.support.is_resource_enabled("cpu"):
names = random.sample(names, 10)
# bpo-31174: Store the names sample to always test the same files.
# It prevents false alarms when hunting reference leaks.
cls.NAMES = names
return names
items = random.sample(items, 10)
return items
def test_files(self):
# get names of files to test
names = self.get_names()
for filename in names:
for item in self.files_to_test:
if test.support.verbose:
print('Testing %s' % filename)
print(f"Testing {item.absolute()}")
# Some f-strings are not correctly round-tripped by
# Tools/parser/unparse.py. See issue 28002 for details.
# We need to skip files that contain such f-strings.
if os.path.basename(filename) in ('test_fstring.py', ):
# Tools/parser/unparse.py. See issue 28002 for details.
# We need to skip files that contain such f-strings.
if item.name in self.skip_files:
if test.support.verbose:
print(f'Skipping {filename}: see issue 28002')
print(f"Skipping {item.absolute()}: see issue 28002")
continue
with self.subTest(filename=filename):
source = read_pyfile(filename)
with self.subTest(filename=item):
source = read_pyfile(item)
self.check_roundtrip(source)
if __name__ == '__main__':
if __name__ == "__main__":
unittest.main()

View file

@ -0,0 +1,4 @@
Expose :func:`ast.unparse` as a function of the :mod:`ast` module that can
be used to unparse an :class:`ast.AST` object and produce a string with code
that would produce an equivalent :class:`ast.AST` object when parsed. Patch
by Pablo Galindo and Batuhan Taskaya.

View file

@ -1,704 +0,0 @@
"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("[")
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 = 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:])