https://stackoverflow.com/questions/48874455/pyparsing-2nd-e

#!/usr/bin/env python
import pyparsing as pp
from pprint import pprint

indentStack = [1]
stmt = pp.Forward()
suite = pp.Group(pp.indentedBlock(stmt, indentStack)).setName("suite") #.setDebug()
command = (pp.Keyword("open") | pp.Keyword("close")).setName("command") #.setDebug()
funcDecl = (pp.Keyword("def") + pp.Word(pp.printables)).setName("function_declaration") #.setDebug()
funcDef = (funcDecl + suite).setName("function_definition") #.setDebug()
stmt << ( funcDef | command)
module_body = pp.OneOrMore(stmt)

code="""\
def process
    open
    close"""

print("example: indentStack: ", indentStack, hex(id(indentStack)))
print("example: funcDef    : ", funcDef)
f1 = funcDef.parseString(code)  ### works fine

indentStack = [1]
# indentStack.pop()

print("example: indentStack: ", indentStack, hex(id(indentStack)))
print("example: funcDef    : ", funcDef)
f2 = funcDef.parseString(code)



Executoion
----------
(py3.6.1) [backend@gc-backend-2 backend]$
(py3.6.1) [backend@gc-backend-2 backend]$ python pp2.py
example: indentStack:  [1] 0x7f77b56ae3c8           <------------ the first instance of the indentStack list
example: funcDef    :  function_definition
checkSubIndent: curCol     :  5
checkSubIndent: indentStack:  0x7f77b56ae3c8
checkSubIndent: indentStack:  [1]
checkSubIndent: indentStack:  [1, 5]  (append)
example: indentStack:  [1] 0x7f77b56b0148           <------------ the NEW instance of the indentStack list!!!
example: funcDef    :  function_definition
checkSubIndent: curCol     :  5
checkSubIndent: indentStack:  0x7f77b56ae3c8        <------------ the first instance of the indentStack list
checkSubIndent: indentStack:  [1, 5]
Traceback (most recent call last):
  File "pp2.py", line 28, in <module>
    f2 = funcDef.parseString(code)
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 1632, in parseString
    raise exc
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 1622, in parseString
    loc, tokens = self._parse( instring, 0 )
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 3395, in parseImpl
    loc, exprtokens = e._parse( instring, loc, doActions )
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 3717, in parseImpl
    return self.expr._parse( instring, loc, doActions, callPreParse=False )
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 3717, in parseImpl
    return self.expr._parse( instring, loc, doActions, callPreParse=False )
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 3395, in parseImpl
    loc, exprtokens = e._parse( instring, loc, doActions )
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 1405, in _parseNoCache
    tokens = fn( instring, tokensStart, retTokens )
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 1049, in wrapper
    ret = func(*args[limit[0]:])
  File "/home/backend/venvs/py3.6.1/lib/python3.6/site-packages/pyparsing.py", line 5321, in checkSubIndent
    raise ParseException(s,l,"not a subentry")
pyparsing.ParseException: not a subentry (at char 16), (line:2, col:5)