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pythonpyparsing

How to define an optional word in pyparse grammar?

I'm parsing sql code objects for the object name and for views I noticed that there are optional keywords that could throw my grammar off. I think I need to be able to define an optional keyword but I have not found a way to do so.

For example

viewDefinition = "CREATE OR REPLACE VIEW" + Word( alphas+"_", alphanums+"_") 
forceviewLine = "CREATE OR REPLACE FORCE VIEW VW_MY_TEST_VIEW"

print(forceviewLine,"->", viewDefinition.parseString(forceviewLine))
viewname = viewDefinition.parseString(forceviewLine)[1]

Because the grammar doesn't fit anymore I'd encounter the following error

pyparsing.ParseException: Expected "CREATE OR REPLACE VIEW" (at char 0), (line:1, col:1)

Is there a way to define an optional keyword on the grammar that could come before the keyword VIEW and that I can get the VW_MY_TEST_VIEW code object name?

Solution

  • I figured it out thought it might be useful for others so I'm answering myself.

    COR = CaselessLiteral('CREATE OR REPLACE') 
optFORCEkw = Optional(CaselessLiteral('FORCE'))
V = CaselessLiteral('VIEW')


forceviewLine = "CREATE OR REPLACE FORCE VIEW VW_MY_TEST_VIEW"
normalviewLine = "CREATE OR REPLACE VIEW VW_MY_TEST_VIEW"

newGrammer2 = COR + optFORCEkw + V + Word( alphas+"_", alphanums+"_") 
print(forceviewLine,"->", newGrammer2.parseString(forceviewLine))
print(normalviewLine,"->", newGrammer2.parseString(normalviewLine))