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"Usage: unparse.py <path to source file>"
import sys
class Unparser:
"""Methods in this class recursively traverse an AST and
output source code for the abstract syntax; original formatting
is disregarged. """
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)
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 _Import(self, t):
self.fill("import ")
first = True
for a in t.names:
if first:
first = False
else:
self.write(", ")
self.write(a.name)
if a.asname:
self.write(" as "+a.asname)
def _Assign(self, t):
self.fill()
for target in t.targets:
self.dispatch(target)
self.write(" = ")
self.dispatch(t.value)
def _ClassDef(self, t):
self.write("\n")
self.fill("class "+t.name)
if t.bases:
self.write("(")
for a in t.bases:
self.dispatch(a)
self.write(", ")
self.write(")")
self.enter()
self.dispatch(t.body)
self.leave()
def _FunctionDef(self, t):
self.write("\n")
self.fill("def "+t.name + "(")
self.dispatch(t.args)
self.enter()
self.dispatch(t.body)
self.leave()
def _If(self, t):
self.fill("if ")
self.dispatch(t.test)
self.enter()
# XXX elif?
self.dispatch(t.body)
self.leave()
if t.orelse:
self.fill("else")
self.enter()
self.dispatch(t.orelse)
self.leave()
# expr
def _Str(self, tree):
self.write(repr(tree.s))
def _Name(self, t):
self.write(t.id)
def _List(self, t):
self.write("[")
for e in t.elts:
self.dispatch(e)
self.write(", ")
self.write("]")
unop = {"Invert":"~", "Not": "not", "UAdd":"+", "USub":"-"}
def _UnaryOp(self, t):
self.write(self.unop[t.op.__class__.__name__])
self.write("(")
self.dispatch(t.operand)
self.write(")")
# others
def _arguments(self, t):
first = True
# XXX t.defaults
for a in t.args:
if first:first = False
else: self.write(", ")
self.dispatch(a)
if t.vararg:
if first:first = False
else: self.write(", ")
self.write("*"+t.vararg)
if t.kwarg:
if first:first = False
else: self.write(", ")
self.write("**"+self.kwarg)
self.write(")")
def roundtrip(filename):
source = open(filename).read()
tree = compile(source, filename, "exec", 0x400)
Unparser(tree)
if __name__=='__main__':
roundtrip(sys.argv[1])
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