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|
| | """Safely evaluate Python string literals without using eval().""" |
| |
|
| | import re |
| |
|
| | simple_escapes = {"a": "\a", |
| | "b": "\b", |
| | "f": "\f", |
| | "n": "\n", |
| | "r": "\r", |
| | "t": "\t", |
| | "v": "\v", |
| | "'": "'", |
| | '"': '"', |
| | "\\": "\\"} |
| |
|
| | def escape(m): |
| | all, tail = m.group(0, 1) |
| | assert all.startswith("\\") |
| | esc = simple_escapes.get(tail) |
| | if esc is not None: |
| | return esc |
| | if tail.startswith("x"): |
| | hexes = tail[1:] |
| | if len(hexes) < 2: |
| | raise ValueError("invalid hex string escape ('\\%s')" % tail) |
| | try: |
| | i = int(hexes, 16) |
| | except ValueError: |
| | raise ValueError("invalid hex string escape ('\\%s')" % tail) from None |
| | else: |
| | try: |
| | i = int(tail, 8) |
| | except ValueError: |
| | raise ValueError("invalid octal string escape ('\\%s')" % tail) from None |
| | return chr(i) |
| |
|
| | def evalString(s): |
| | assert s.startswith("'") or s.startswith('"'), repr(s[:1]) |
| | q = s[0] |
| | if s[:3] == q*3: |
| | q = q*3 |
| | assert s.endswith(q), repr(s[-len(q):]) |
| | assert len(s) >= 2*len(q) |
| | s = s[len(q):-len(q)] |
| | return re.sub(r"\\(\'|\"|\\|[abfnrtv]|x.{0,2}|[0-7]{1,3})", escape, s) |
| |
|
| | def test(): |
| | for i in range(256): |
| | c = chr(i) |
| | s = repr(c) |
| | e = evalString(s) |
| | if e != c: |
| | print(i, c, s, e) |
| |
|
| |
|
| | if __name__ == "__main__": |
| | test() |
| |
|
