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pythonpython-3.xpyparsing

Railroad Diagrams don't show expression names

Using pyparsing version 3.0.0a2 to generate some railroad diagrams I end up with sub-diagrams named Group or Unnamed 1, 2, etc. No need to says that several different expressions have the name Group. How can we specify the wanted names for each expression?

enter image description here

Solution

  • Be sure that you are calling setName on the significant expressions within your grammar.

    This expression will show up as Unnamed:

    # US social security numbers are of the form 000-00-0000
ssn = Word(nums, exact=3) + '-' + Word(nums, exact=2) + '-' + Word(nums, exact=4)

    unnamed ssn railroad diagram

    setName attaches a name to the expression:

    ssn = (Word(nums, exact=3) 
       + '-' + Word(nums, exact=2) 
       + '-' + Word(nums, exact=4)).setName("social_security_number")

    named ssn railroad diagram

    Keep in mind the distinction between setName and setResultsName:

    • setName attaches a name to the expression itself (a concept made more clear now with the railroad diagram support)

    • setResultsName designates a name to be attached to the parsed results extracted by this expression

    An expression will have just one name, such as Word(nums) is an "integer". But that expression may be used in several places within a grammar, and so could have multiple results names. See how real is used multiple times in this example:

    real = Regex(r"\d+\.\d+").setName("real number")
lat_long = "(" + Char("NS") + real("latitude") + "," + Char("EW") + real("longitude") + ")"