| Tim Peters | 710ab3b | 2006-02-28 18:30:36 +0000 | [diff] [blame] | 1 | "Usage: unparse.py <path to source file>"
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| 2 | import sys
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| 3 |
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| 4 | class Unparser:
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| 5 | """Methods in this class recursively traverse an AST and
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| 6 | output source code for the abstract syntax; original formatting
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| 7 | is disregarged. """
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| 8 |
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| 9 | def __init__(self, tree, file = sys.stdout):
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| 10 | """Unparser(tree, file=sys.stdout) -> None.
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| 11 | Print the source for tree to file."""
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| 12 | self.f = file
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| 13 | self._indent = 0
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| 14 | self.dispatch(tree)
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| 15 | self.f.flush()
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| 16 |
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| 17 | def fill(self, text = ""):
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| 18 | "Indent a piece of text, according to the current indentation level"
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| 19 | self.f.write("\n"+" "*self._indent + text)
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| 20 |
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| 21 | def write(self, text):
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| 22 | "Append a piece of text to the current line."
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| 23 | self.f.write(text)
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| 24 |
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| 25 | def enter(self):
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| 26 | "Print ':', and increase the indentation."
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| 27 | self.write(":")
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| 28 | self._indent += 1
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| 29 |
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| 30 | def leave(self):
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| 31 | "Decrease the indentation level."
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| 32 | self._indent -= 1
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| 33 |
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| 34 | def dispatch(self, tree):
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| 35 | "Dispatcher function, dispatching tree type T to method _T."
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| 36 | if isinstance(tree, list):
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| 37 | for t in tree:
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| 38 | self.dispatch(t)
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| 39 | return
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| 40 | meth = getattr(self, "_"+tree.__class__.__name__)
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| 41 | meth(tree)
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| 42 |
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| 43 |
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| 44 | ############### Unparsing methods ######################
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| 45 | # There should be one method per concrete grammar type #
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| 46 | # Constructors should be grouped by sum type. Ideally, #
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| 47 | # this would follow the order in the grammar, but #
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| 48 | # currently doesn't. #
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| 49 | ########################################################
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| 50 |
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| 51 | def _Module(self, tree):
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| 52 | for stmt in tree.body:
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| 53 | self.dispatch(stmt)
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| 54 |
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| 55 | # stmt
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| 56 | def _Expr(self, tree):
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| 57 | self.fill()
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| 58 | self.dispatch(tree.value)
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| 59 |
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| 60 | def _Import(self, t):
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| 61 | self.fill("import ")
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| 62 | first = True
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| 63 | for a in t.names:
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| 64 | if first:
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| 65 | first = False
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| 66 | else:
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| 67 | self.write(", ")
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| 68 | self.write(a.name)
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| 69 | if a.asname:
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| 70 | self.write(" as "+a.asname)
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| 71 |
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| 72 | def _Assign(self, t):
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| 73 | self.fill()
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| 74 | for target in t.targets:
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| 75 | self.dispatch(target)
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| 76 | self.write(" = ")
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| 77 | self.dispatch(t.value)
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| 78 |
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| 79 | def _ClassDef(self, t):
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| 80 | self.write("\n")
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| 81 | self.fill("class "+t.name)
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| 82 | if t.bases:
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| 83 | self.write("(")
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| 84 | for a in t.bases:
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| 85 | self.dispatch(a)
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| 86 | self.write(", ")
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| 87 | self.write(")")
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| 88 | self.enter()
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| 89 | self.dispatch(t.body)
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| 90 | self.leave()
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| 91 |
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| 92 | def _FunctionDef(self, t):
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| 93 | self.write("\n")
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| 94 | self.fill("def "+t.name + "(")
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| 95 | self.dispatch(t.args)
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| 96 | self.enter()
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| 97 | self.dispatch(t.body)
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| 98 | self.leave()
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| 99 |
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| 100 | def _If(self, t):
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| 101 | self.fill("if ")
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| 102 | self.dispatch(t.test)
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| 103 | self.enter()
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| 104 | # XXX elif?
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| 105 | self.dispatch(t.body)
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| 106 | self.leave()
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| 107 | if t.orelse:
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| 108 | self.fill("else")
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| 109 | self.enter()
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| 110 | self.dispatch(t.orelse)
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| 111 | self.leave()
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| 112 |
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| 113 | # expr
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| 114 | def _Str(self, tree):
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| 115 | self.write(repr(tree.s))
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| 116 |
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| 117 | def _Name(self, t):
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| 118 | self.write(t.id)
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| 119 |
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| 120 | def _List(self, t):
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| 121 | self.write("[")
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| 122 | for e in t.elts:
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| 123 | self.dispatch(e)
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| 124 | self.write(", ")
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| 125 | self.write("]")
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| 126 |
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| 127 | unop = {"Invert":"~", "Not": "not", "UAdd":"+", "USub":"-"}
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| 128 | def _UnaryOp(self, t):
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| 129 | self.write(self.unop[t.op.__class__.__name__])
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| 130 | self.write("(")
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| 131 | self.dispatch(t.operand)
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| 132 | self.write(")")
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| 133 |
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| 134 | # others
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| 135 | def _arguments(self, t):
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| 136 | first = True
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| 137 | # XXX t.defaults
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| 138 | for a in t.args:
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| 139 | if first:first = False
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| 140 | else: self.write(", ")
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| 141 | self.dispatch(a)
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| 142 | if t.vararg:
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| 143 | if first:first = False
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| 144 | else: self.write(", ")
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| 145 | self.write("*"+t.vararg)
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| 146 | if t.kwarg:
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| 147 | if first:first = False
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| 148 | else: self.write(", ")
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| 149 | self.write("**"+self.kwarg)
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| 150 | self.write(")")
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| 151 |
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| 152 | def roundtrip(filename):
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| 153 | source = open(filename).read()
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| 154 | tree = compile(source, filename, "exec", 0x400)
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| 155 | Unparser(tree)
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| 156 |
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| 157 | if __name__=='__main__':
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| 158 | roundtrip(sys.argv[1])
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