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Using pyparsing

The day after I hyped the Getting Started with PyParsing book, I got to use it. Here’s the script :

  from pyparsing import SkipTo, Suppress, CaselessLiteral
  import glob

  # Example to match
  # delete from TABLENAME
  # where       CUSTOMER_ID = 'INTERNAL';

  table_name = SkipTo("where")
  where_clause = SkipTo(';')

  delete_stmt = Suppress("delete") +  Suppress("from") + table_name
     + Suppress("where") + where_clause + Suppress(";")

  for filename in glob.glob('*.sql'):
      f = open(filename)
      print '-- ', filename, ':'
      for tokens, start,end in delete_stmt.scanString(lines):
          print 'select * from ' + tokens[0] + ' where ' + tokens[1] + ';'

This loops over all the files called *.sql in the current directory. Then it checks if there are any matches to the delete_stmt variable. So it has to match the literal “delete” and then the literal “from”. These are not put in the output, because they are in a Suppress() object.

After that we select everything up to ‘where’ as the table_name. Then the literal “where” has to be present. Everything up to the semicolon is then read into the where_clause variable.

Lastly the table name and where clause are used to create a select statement.

PS : The code was changed so that this

  from pyparsing import *

became :

  from pyparsing import SkipTo, Suppress, CaselessLiteral

This way we don’t pollute the current namespace.