/usr/lib/python2.7/lib2to3/pgen2/literals.py is in libpython2.7-stdlib 2.7.11-7ubuntu1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 | # Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.
"""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)
else:
try:
i = int(tail, 8)
except ValueError:
raise ValueError("invalid octal string escape ('\\%s')" % tail)
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()
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