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#!/usr/bin/python
#
# Copyright 2011 Nick Mathewson, Michael Stone
#
# You may do anything with this work that copyright law would normally
# restrict, so long as you retain the above notice(s) and this license
# in all redistributed copies and derived works. There is no warranty.
"""
>>> base = Environ(foo=99, bar=600)
>>> derived1 = Environ(parent=base, bar=700, quux=32)
>>> base["foo"]
99
>>> sorted(base.keys())
['bar', 'foo']
>>> derived1["foo"]
99
>>> base["bar"]
600
>>> derived1["bar"]
700
>>> derived1["quux"]
32
>>> sorted(derived1.keys())
['bar', 'foo', 'quux']
>>> class Specialized(Environ):
... def __init__(self, p=None, **kw):
... Environ.__init__(self, p, **kw)
... self._n_calls = 0
... def _get_expensive_value(self, me):
... self._n_calls += 1
... return "Let's pretend this is hard to compute"
...
>>> s = Specialized(base, quux="hi")
>>> s["quux"]
'hi'
>>> s['expensive_value']
"Let's pretend this is hard to compute"
>>> s['expensive_value']
"Let's pretend this is hard to compute"
>>> s._n_calls
1
>>> sorted(s.keys())
['bar', 'expensive_value', 'foo', 'quux']
>>> bt = _BetterTemplate("Testing ${hello}, $goodbye$$, $foo , ${a:b:c}")
>>> bt.safe_substitute({'a:b:c': "4"}, hello=1, goodbye=2, foo=3)
'Testing 1, 2$, 3 , 4'
>>> t = Template("${include:/dev/null} $hi_there")
>>> sorted(t.freevars())
['hi_there']
>>> t.format(dict(hi_there=99))
' 99'
>>> t2 = Template("X$${include:$fname} $bar $baz")
>>> t2.format(dict(fname="/dev/null", bar=33, baz="$foo", foo=1337))
'X 33 1337'
>>> sorted(t2.freevars({'fname':"/dev/null"}))
['bar', 'baz', 'fname']
"""
from __future__ import with_statement
import string
import os
import re
#class _KeyError(KeyError):
# pass
_KeyError = KeyError
class _DictWrapper:
def __init__(self, parent=None):
self._parent = parent
def __getitem__(self, key):
try:
return self._getitem(key)
except KeyError:
pass
if self._parent is None:
raise _KeyError(key)
try:
return self._parent[key]
except KeyError:
raise _KeyError(key)
class Environ(_DictWrapper):
def __init__(self, parent=None, **kw):
_DictWrapper.__init__(self, parent)
self._dict = kw
self._cache = {}
def _getitem(self, key):
try:
return self._dict[key]
except KeyError:
pass
try:
return self._cache[key]
except KeyError:
pass
fn = getattr(self, "_get_%s"%key, None)
if fn is not None:
try:
self._cache[key] = rv = fn(self)
return rv
except _KeyError:
raise KeyError(key)
raise KeyError(key)
def __setitem__(self, key, val):
self._dict[key] = val
def keys(self):
s = set()
s.update(self._dict.keys())
s.update(self._cache.keys())
if self._parent is not None:
s.update(self._parent.keys())
s.update(name[5:] for name in dir(self) if name.startswith("_get_"))
return s
class IncluderDict(_DictWrapper):
def __init__(self, parent, includePath=(".",)):
_DictWrapper.__init__(self, parent)
self._includePath = includePath
def _getitem(self, key):
if not key.startswith("include:"):
raise KeyError(key)
filename = key[len("include:"):]
if os.path.isabs(filename):
with open(filename, 'r') as f:
return f.read()
for elt in self._includePath:
fullname = os.path.join(elt, filename)
if os.path.exists(fullname):
with open(fullname, 'r') as f:
return f.read()
raise KeyError(key)
class _BetterTemplate(string.Template):
idpattern = r'[a-z0-9:_/\.\-]+'
def __init__(self, template):
string.Template.__init__(self, template)
class _FindVarsHelper:
def __init__(self, dflts):
self._dflts = dflts
self._vars = set()
def __getitem__(self, var):
self._vars.add(var)
try:
return self._dflts[var]
except KeyError:
return ""
class Template:
MAX_ITERATIONS = 32
def __init__(self, pattern, includePath=(".",)):
self._pat = pattern
self._includePath = includePath
def freevars(self, defaults=None):
if defaults is None:
defaults = {}
d = _FindVarsHelper(defaults)
self.format(d)
return d._vars
def format(self, values):
values = IncluderDict(values, self._includePath)
orig_val = self._pat
nIterations = 0
while True:
v = _BetterTemplate(orig_val).substitute(values)
if v == orig_val:
return v
orig_val = v
nIterations += 1
if nIterations > self.MAX_ITERATIONS:
raise ValueError("Too many iterations in expanding template!")
if __name__ == '__main__':
import sys
if len(sys.argv) == 1:
import doctest
doctest.testmod()
print "done"
else:
for fn in sys.argv[1:]:
with open(fn, 'r') as f:
t = Template(f.read())
print fn, t.freevars()
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