| Tim Peters | 400cbc3 | 2006-02-28 18:44:41 +0000 | [diff] [blame^] | 1 | "Usage: unparse.py <path to source file>" |
| 2 | import sys |
| 3 | |
| 4 | class Unparser: |
| 5 | """Methods in this class recursively traverse an AST and |
| 6 | output source code for the abstract syntax; original formatting |
| 7 | is disregarged. """ |
| 8 | |
| 9 | def __init__(self, tree, file = sys.stdout): |
| 10 | """Unparser(tree, file=sys.stdout) -> None. |
| 11 | Print the source for tree to file.""" |
| 12 | self.f = file |
| 13 | self._indent = 0 |
| 14 | self.dispatch(tree) |
| 15 | self.f.flush() |
| 16 | |
| 17 | def fill(self, text = ""): |
| 18 | "Indent a piece of text, according to the current indentation level" |
| 19 | self.f.write("\n"+" "*self._indent + text) |
| 20 | |
| 21 | def write(self, text): |
| 22 | "Append a piece of text to the current line." |
| 23 | self.f.write(text) |
| 24 | |
| 25 | def enter(self): |
| 26 | "Print ':', and increase the indentation." |
| 27 | self.write(":") |
| 28 | self._indent += 1 |
| 29 | |
| 30 | def leave(self): |
| 31 | "Decrease the indentation level." |
| 32 | self._indent -= 1 |
| 33 | |
| 34 | def dispatch(self, tree): |
| 35 | "Dispatcher function, dispatching tree type T to method _T." |
| 36 | if isinstance(tree, list): |
| 37 | for t in tree: |
| 38 | self.dispatch(t) |
| 39 | return |
| 40 | meth = getattr(self, "_"+tree.__class__.__name__) |
| 41 | meth(tree) |
| 42 | |
| 43 | |
| 44 | ############### Unparsing methods ###################### |
| 45 | # There should be one method per concrete grammar type # |
| 46 | # Constructors should be grouped by sum type. Ideally, # |
| 47 | # this would follow the order in the grammar, but # |
| 48 | # currently doesn't. # |
| 49 | ######################################################## |
| 50 | |
| 51 | def _Module(self, tree): |
| 52 | for stmt in tree.body: |
| 53 | self.dispatch(stmt) |
| 54 | |
| 55 | # stmt |
| 56 | def _Expr(self, tree): |
| 57 | self.fill() |
| 58 | self.dispatch(tree.value) |
| 59 | |
| 60 | def _Import(self, t): |
| 61 | self.fill("import ") |
| 62 | first = True |
| 63 | for a in t.names: |
| 64 | if first: |
| 65 | first = False |
| 66 | else: |
| 67 | self.write(", ") |
| 68 | self.write(a.name) |
| 69 | if a.asname: |
| 70 | self.write(" as "+a.asname) |
| 71 | |
| 72 | def _Assign(self, t): |
| 73 | self.fill() |
| 74 | for target in t.targets: |
| 75 | self.dispatch(target) |
| 76 | self.write(" = ") |
| 77 | self.dispatch(t.value) |
| 78 | |
| 79 | def _ClassDef(self, t): |
| 80 | self.write("\n") |
| 81 | self.fill("class "+t.name) |
| 82 | if t.bases: |
| 83 | self.write("(") |
| 84 | for a in t.bases: |
| 85 | self.dispatch(a) |
| 86 | self.write(", ") |
| 87 | self.write(")") |
| 88 | self.enter() |
| 89 | self.dispatch(t.body) |
| 90 | self.leave() |
| 91 | |
| 92 | def _FunctionDef(self, t): |
| 93 | self.write("\n") |
| 94 | self.fill("def "+t.name + "(") |
| 95 | self.dispatch(t.args) |
| 96 | self.enter() |
| 97 | self.dispatch(t.body) |
| 98 | self.leave() |
| 99 | |
| 100 | def _If(self, t): |
| 101 | self.fill("if ") |
| 102 | self.dispatch(t.test) |
| 103 | self.enter() |
| 104 | # XXX elif? |
| 105 | self.dispatch(t.body) |
| 106 | self.leave() |
| 107 | if t.orelse: |
| 108 | self.fill("else") |
| 109 | self.enter() |
| 110 | self.dispatch(t.orelse) |
| 111 | self.leave() |
| 112 | |
| 113 | # expr |
| 114 | def _Str(self, tree): |
| 115 | self.write(repr(tree.s)) |
| 116 | |
| 117 | def _Name(self, t): |
| 118 | self.write(t.id) |
| 119 | |
| 120 | def _List(self, t): |
| 121 | self.write("[") |
| 122 | for e in t.elts: |
| 123 | self.dispatch(e) |
| 124 | self.write(", ") |
| 125 | self.write("]") |
| 126 | |
| 127 | unop = {"Invert":"~", "Not": "not", "UAdd":"+", "USub":"-"} |
| 128 | def _UnaryOp(self, t): |
| 129 | self.write(self.unop[t.op.__class__.__name__]) |
| 130 | self.write("(") |
| 131 | self.dispatch(t.operand) |
| 132 | self.write(")") |
| 133 | |
| 134 | # others |
| 135 | def _arguments(self, t): |
| 136 | first = True |
| 137 | # XXX t.defaults |
| 138 | for a in t.args: |
| 139 | if first:first = False |
| 140 | else: self.write(", ") |
| 141 | self.dispatch(a) |
| 142 | if t.vararg: |
| 143 | if first:first = False |
| 144 | else: self.write(", ") |
| 145 | self.write("*"+t.vararg) |
| 146 | if t.kwarg: |
| 147 | if first:first = False |
| 148 | else: self.write(", ") |
| 149 | self.write("**"+self.kwarg) |
| 150 | self.write(")") |
| 151 | |
| 152 | def roundtrip(filename): |
| 153 | source = open(filename).read() |
| 154 | tree = compile(source, filename, "exec", 0x400) |
| 155 | Unparser(tree) |
| 156 | |
| 157 | if __name__=='__main__': |
| 158 | roundtrip(sys.argv[1]) |