cpython/Tools/modulator/varsubst.py

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#
# Variable substitution. Variables are $delimited$
#
import string
import regex
import regsub
error = 'varsubst.error'
class Varsubst:
def __init__(self, dict):
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self.dict = dict
self.prog = regex.compile('\$[a-zA-Z0-9_]*\$')
self.do_useindent = 0
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def useindent(self, onoff):
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self.do_useindent = onoff
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def subst(self, str):
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rv = ''
while 1:
pos = self.prog.search(str)
if pos < 0:
return rv + str
if pos:
rv = rv + str[:pos]
str = str[pos:]
len = self.prog.match(str)
if len == 2:
# Escaped dollar
rv = rv + '$'
str = str[2:]
continue
name = str[1:len-1]
str = str[len:]
if not self.dict.has_key(name):
raise error, 'No such variable: '+name
value = self.dict[name]
if self.do_useindent and '\n' in value:
value = self._modindent(value, rv)
rv = rv + value
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def _modindent(self, value, old):
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lastnl = string.rfind(old, '\n', 0) + 1
lastnl = len(old) - lastnl
sub = '\n' + (' '*lastnl)
return regsub.gsub('\n', sub, value)
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def _test():
import sys
import os
sys.stderr.write('-- Copying stdin to stdout with environment map --\n')
c = Varsubst(os.environ)
c.useindent(1)
d = sys.stdin.read()
sys.stdout.write(c.subst(d))
sys.exit(1)
if __name__ == '__main__':
_test()